Rescission of the Greenhouse Gas Endangerment Finding and Motor Vehicle Greenhouse Gas Emission Standards Under the Clean Air Act

A. Does this action apply to me?

B. Where can I get a copy of this document and other related information?

C. Judicial Review and Administrative Review II. Executive Summary

A. Introduction

B. Need for Regulatory Action

C. Summary of Comments and Updates From the Proposal in This Final Action

1. Issues Raised Regarding the Rulemaking Process

2. Updates From the Proposal in This Final Action III. Background

A. The EPA's Historical Approach to CAA Section 202(a)(1)

B. Petitions for Rulemaking and Massachusetts v. EPA

C. The 2009 Endangerment Finding

D. Implementation of the 2009 Endangerment Finding

E. Reconsideration of the 2009 Endangerment Finding IV. Legal Framework for Action

A. Rescission of the Endangerment Finding

1. Issues Raised Regarding Rescission Authority

2. Issues Raised Regarding Reliance Interests

B. Repeal of New Motor Vehicle and Engine GHG Emission Standards V. Rescission of the Endangerment Finding

A. Best Reading of CAA Section 202(a)(1)

1. Final Rationale

2. Summary of Comments and Updates Since Proposal

B. Lack of Clear Congressional Authorization

1. Final Rationale

2. Summary of Comments and Updates Since Proposal

C. Eliminating GHG Emissions From Motor Vehicles and Engines Would Be Futile

1. Final Rationale

2. Summary of Comments and Responses and Updates to the Final Action VI. Additional Proposed Bases for Rescission of the Endangerment Finding and Repeal of GHG Emission Standards the Agency Is Not Finalizing at This Time

A. Climate Science Alternative Basis

B. There Is No Requisite Technology for Light- and Medium-Duty Vehicles That Meaningfully Addresses the Identified Dangers of the Six “Well-Mixed” GHGs

C. There Is No Requisite Technology for Heavy-Duty Vehicles That Addresses the Identified Dangers of the Six “Well-Mixed” GHGs

D. More Expensive New Vehicles Prevent Americans From Purchasing New Vehicles That Are More Efficient, Safer, and Emit Fewer GHGs VII. Repeal of New Motor Vehicle and Engine GHG Emission Standards

A. Scope and Impacts of Repealing the GHG Emission Standards

B. Light- and Medium-Duty Vehicle GHG Program

1. Background on the Light- and Medium-Duty Vehicle GHG Program

2. Summary of Comments and Updates to the Light- and Medium-Duty Programs

3. Changes to the Light- and Medium-Duty Vehicle GHG Regulations

C. Heavy-Duty Engine and Vehicle GHG Program

1. Background on the Heavy-Duty Engine and Vehicle GHG Program

2. Summary of Comments and Updates to the Heavy-Duty Engine and Vehicle Programs

3. Changes to the Heavy-Duty Engine and Vehicle GHG Regulations VIII. Statutory and Executive Order Reviews

A. Executive Order 12866: Regulatory Planning and Review and Executive Order 14094: Modernizing Regulatory Review

B. Executive Order 14192: Unleashing Prosperity Through Deregulation

C. Paperwork Reduction Act (PRA)

1. 2024 LD and MD Multi-Pollutant Emission Standards Rule

2. 2024 HD GHG Emission Standards Rule

3. Nonroad Compression-Ignition Engines and On-Highway Heavy- Duty Engines, Supporting Statement for Information Collection Request (March 2023 Revision)

D. Regulatory Flexibility Act (RFA)

E. Unfunded Mandates Reform Act (UMRA)

F. Executive Order 13132: Federalism

G. Executive Order 13175: Consultation and Coordination With Indian Tribal Governments

H. Executive Order 13045: Protection of Children From Environmental Health Risks and Safety Risks

I. Executive Order 13211: Actions Concerning Regulations That Significantly Affect Energy Supply, Distribution, or Use

J. National Technology Transfer and Advancement Act (NTTAA) and 1 CFR Part 51

K. Congressional Review Act (CRA)

Under CAA section 307(b)(1), judicial review of this final action is available only by filing a petition for review in the United States Court of Appeals for the District of Columbia Circuit (D.C. Circuit) by April 20, 2026. Under CAA section 307(b)(2), the requirements established by this final action may not be challenged separately in any civil or criminal proceedings brought by the EPA to enforce the requirements.

CAA section 307(d)(7)(B) further provides that “[o]nly an objection to a rule or procedure which was raised with reasonable specificity during the period for public comment (including any public hearing) may be raised during judicial review.” This section also provides a mechanism for the EPA to convene a proceeding for reconsideration “[i]f the person raising an objection can demonstrate to the EPA that it was impracticable to raise such objection within [the period for public comment] or if the grounds for such objection arose after the period for public comment, (but within the time specified for judicial review) and if such objection is of central relevance to the outcome of the rule.” Any person seeking to make such a demonstration to us should submit a Petition for Reconsideration to the Office of the Administrator, U.S. Environmental Protection Agency, Room 3000, WJC South Building, 1200 Pennsylvania Ave. NW, Washington, DC 20460, with a copy to both the person(s) listed in the preceding FOR FURTHER INFORMATION CONTACT section, and the Associate General Counsel for the Air and Radiation Law Office, Office of General Counsel (Mail Code 2344A), U.S. Environmental Protection Agency, 1200 Pennsylvania Ave. NW, Washington, DC 20460.

In this final action, the EPA rescinds the Administrator's 2009 standalone decision entitled “Endangerment and Cause or Contribute Findings for Greenhouse Gases Under Section 202(a) of the Clean Air Act,” 74 FR 66496 (Dec. 15, 2009) (“Endangerment Finding”) and repeals all GHG emission standards for light-duty (LD), medium-duty (MD), and heavy-duty (HD) vehicles and engines manufactured or imported into the United States (U.S.) for model years (MY) 2012 to 2027 and beyond. Upon review of the underlying actions, recent decisions by the U.S. Supreme Court, and the robust public response to the proposal, the EPA concludes that we lack statutory authority to maintain this novel and transformative regulatory program. The appropriate policy response to global climate change concerns is a decision vested in Congress, and Congress did not decide the Nation's policy response to these concerns when it enacted CAA section 202(a)(1) to address domestic air pollution problems nearly sixty years ago, or in any subsequent amendment thereto. Relatedly, the EPA concludes that regulating GHG emissions from new motor vehicles and engines under CAA section 202(a)(1) has no material impact on global climate change concerns animating the Agency's regulatory efforts since 2009, much less the adverse public health or welfare impacts attributed to such global climate trends. Climate impact modeling submitted during the public comment period, and confirmed by our own analysis, demonstrates that even the complete elimination of all GHG emissions from all new and existing vehicles in the U.S. would have only de minimis impacts that fall well within the standard margin of error for global temperature and sea level measurement. This evidence further supports our conclusion that the regulation of GHG emissions falls outside the scope of air pollution problems Congress addressed when enacting CAA section 202(a)(1) and, separately, leads us to conclude that maintaining GHG emission standards under CAA section 202(a)(1) would be unreasonable given their futility and the immense burdens they place on regulated parties, consumers, and the economy.

The EPA recognizes the gravity of this decision to the many stakeholders who submitted comments for and against to the proposal, including with respect to global climate change concerns and the burdens of our GHG regulatory program on manufacturers, auto workers, and American consumer choice and affordability. We closely reviewed the diverse array of scientific and technical information submitted in response to the proposal. The Administrator continues to harbor concerns regarding the scientific analysis contained in the Endangerment Finding, including because the decision severed the statutory analysis in multiple respects to assert the power to regulate GHG emissions in response to global climate change concerns. However, the Administrator is not basing this action on a new finding under CAA section 202(a)(1). Rather, we conclude that the EPA lacks statutory authority to resolve these questions under CAA section 202(a)(1). As recently as 2008, the Agency correctly understood that the statute was enacted to control air pollution that threatens health and welfare through local and regional exposure, and that launching a GHG emissions program under this authority would result in an unprecedented expansion of regulatory power with profound adverse effects on the economy and American households. With this final action, we return to fundamental principles governing decision-making within our democratic system: “Agencies have only those powers given to them by Congress,” West Virginia v. EPA, 597 U.S. 697, 723 (2022), and “the scope of an agency's own power” is determined not by deference to asserted expertise, but by “the best reading of the statute,” which is fixed at the time of enactment. Loper Bright Enters. v. Raimondo, 603 U.S. 369, 400-01 (2024).

In 2009, the EPA took the unprecedented step of asserting authority to regulate GHG emissions in a standalone action that broke new ground and launched the Agency into a course of regulation that fundamentally reshaped many aspects of the Nation's economic and social life.\1\ In the Endangerment Finding, we interpreted CAA section 202(a)(1) for the first time to authorize regulation of domestic emissions from new motor vehicles and engines based on global climate change concerns rather than air pollution that endangers public health or welfare

through local or regional exposure. 74 FR 66526-27. We relied on that interpretation to define both the relevant “air pollution” and the relevant “air pollutant” as the combination of six “well-mixed GHGs”--carbon dioxide (CO2), methane, nitrous oxide (N2O), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF6)--while reserving the right to include additional “climate forcers” in these definitions in the future. 74 FR 66516-17, 66536-37. We also asserted that because the statute is “silent on [the] issue,” CAA section 202(a)(1) grants “procedural discretion” to issue standalone findings that trigger a duty to regulate without considering the standards that must be issued in response. 74 FR 66501-02. The Administrator exercised this newfound discretion to make separate findings, without analyzing or promulgating any emission standards, that elevated global concentrations in the upper atmosphere of the six “well-mixed GHGs” constitute “air pollution” that may reasonably be anticipated to endanger public health and welfare, 74 FR 66516-36, and that GHG emissions from all potential classes of motor vehicles and engines contribute to such elevated global concentrations of GHGs in the upper atmosphere and therefore to air pollution that endangers public health and welfare, 74 FR 66536-45.

\1\ See also “Endangerment and Cause or Contribute Findings for Greenhouse Gases Under Section 202(a) of the Clean Air Act: EPA's Response to Public Comments” (“EF RTC”), available in a Memorandum to Docket entitled “EPA's Response to Public Comments on the 2009 Endangerment and Cause or Contribute Findings for Greenhouse Gases: Volumes 1-11,” Document ID EPA-HQ-OAR-2025-0149.

With respect to endangerment, the Administrator found that global concentrations of six “well-mixed” GHGs from all foreign and domestic sources “constitute the largest anthropogenic driver of climate change” and attributed climate change impacts to global GHG concentrations. 74 FR 66517. Next, the Administrator summarized literature reviews finding that climate change “can increase the risk of morbidity and mortality” indirectly through increased global temperature, air quality effects, and effects on extreme weather events and can impact welfare indirectly through impacts on sea level rise and coastal areas, food production and agriculture, forestry, water resources, energy, infrastructure, and settlements, and ecosystems and wildlife. 74 FR 66523-35. On that basis, the Administrator found that global concentrations of six “well-mixed” GHGs constitute “air pollution” that endangers public health and welfare. 74 FR 66516. For purposes of this preamble, we use the phrase “global climate change concerns” to refer to the public health and welfare risks the Administrator associated with global climate change in the Endangerment Finding and subsequent actions since 2009.

With respect to causation or contribution, the Administrator used annual emissions data for existing motor vehicles and engines from 2005 to project that all potential classes of new motor vehicles and engines would emit four GHGs--CO2, methane, N2O, and HFCs--that collectively amounted to 4.3 percent of annual global GHG emissions and implicitly would continue in future years. 74 FR 66543. The Administrator acknowledged that a greater degree of contribution would usually be required to meet the statute's contribution element “when addressing a more typical local or regional air pollution problem.” 74 FR 66539. Nevertheless, asserting discretion to interpret the ambiguous term “contribute,” the Administrator found that the “unique” nature of global climate change meant that “contributors must do their part even if their contributions to the global climate change problem, measured in terms of percentage, are smaller than typically encountered when tackling solely regional or local environmental issues.” 74 FR 66542-43. In other words, the Administrator justified the Endangerment Finding on the theory that although the situation was “unique” and the “contribution” of domestic new motor vehicles and engines was not in line with the Agency's prior course of regulation under CAA section 202(a)(1), action was needed because all source categories and all other nations must “do their part” to avoid “a tragedy of the commons.” Id. On that basis, the Administrator found that annual emissions from new motor vehicles and engines “contributed” to the “air pollution,” defined anew for those purposes as the accumulated global concentrations of the six “well-mixed” GHGs, that endangered public health and welfare by giving rise to global climate change concerns. 74 FR 66537.

The EPA subsequently relied on the Endangerment Finding to impose increasingly stringent GHG emission standards for new motor vehicles and engines and to attempt, largely without success, to extend the GHG initiative into additional CAA programs. In Utility Air Regulatory Group v. EPA, 573 U.S. 302 (2014) (UARG), the Supreme Court largely rejected our attempt to extend GHG emission standards to stationary sources subject to Title I and Title V requirements as exceeding our authority under the CAA, including because we admitted that applying the statutory scheme as written to GHG emissions from most covered stationary sources would be unworkable and attempted to rewrite the statute by regulation. And in West Virginia v. EPA, 597 U.S. 697 (2022), the Court vacated our attempt to shift the power grid away from using fossil fuels through GHG standards for existing power plants under CAA section 111(d). The Court held in both cases that the agency actions at issue implicated the major questions doctrine and that Congress must clearly authorize agencies to take actions that decide major questions of policy. Nevertheless, the EPA continued to retain and expand GHG emission standards for new motor vehicles and engines that impose billions of dollars in annual compliance costs on American businesses and consumers and reflect an increasing trend toward forcing a transition to the use of electric vehicles (EVs) rather than gasoline- or diesel-fueled motor vehicles and engines.\2\ Meanwhile, global GHG concentrations in the upper atmosphere have continued to rise, driven primarily by increased emissions from foreign sources,\3\ all without producing the degree of adverse impacts to public health and welfare in the U.S. anticipated in the 2009 Endangerment Finding.\4\

\2\ The EPA is not relying on the Regulatory Impact Analysis (RIA) prepared pursuant to Executive Order (E.O.) 12866 in any of the bases for this final action. Except where expressly stated, none of the legal bases for repeal in section V of this preamble reflect cost considerations, which are not relevant for purposes of this final action in determining the best reading of CAA section 202(a)(1). For the limited instances in which cost is relevant as a general consideration, we discuss cost separately from, and do not rely upon, the RIA prepared pursuant to E.O. 12866.

\3\ Crippa, M. et al. (2023). GHG emissions of all world countries. Publications Office of the European Union: https://doi.org/10.2760/953322.

\4\ The EPA is not relying on new findings by the Administrator with respect to global climate change concerns under CAA section 202(a)(1) as a basis for the rescission or repeals and is not finalizing the alternative basis set out in section IV.B of the preamble to the proposed rule. We are rescinding the Endangerment Finding and repealing all associated GHG emission standards for the reasons discussed in this preamble, which make it unnecessary and inappropriate to resolve outstanding scientific questions regarding global climate change concerns in the regulatory context of CAA section 202(a)(1). Nevertheless, the bases for this final action should not be understood as an additional endorsement or ratification of the scientific analysis in the Endangerment Finding. See section VI.A of this preamble for further discussion.

Upon reconsideration, the EPA now acknowledges that the Endangerment Finding and subsequent regulations exceeded the Agency's statutory authority under CAA section 202(a)(1). These actions rested on a profound misreading of the Supreme Court's decision in Massachusetts v. EPA, 549 U.S. 497 (2007), which vacated the denial of a petition for rulemaking in

which we concluded that CO2 and three other GHGs fell outside the statutory definition of “air pollutant” in CAA section 302(g) and should not be regulated for additional policy reasons. As we later explained in a 2008 advance notice of proposed rulemaking entitled “Regulating Greenhouse Gas Emissions Under the Clean Air Act,” the statute was “enacted to control regional pollutants that cause direct health effects,” and regulating GHG emissions under its provisions “could result in an unprecedented expansion of EPA authority that would have a profound effect on virtually every sector of the economy and touch every household in the land.” 73 FR 44354, 44355 (July 30, 2008) (“2008 ANPRM”). Intervening legal developments reinforce our conclusion that Congress did not decide the Nation's policy response to global climate change concerns in CAA section 202(a)(1), let alone clearly authorize the EPA to make that policy choice by prescribing emission standards that force a transition to EVs. Nor does climate impact modeling suggest that the EPA's initiative has been anything but futile, which further supports the conclusion that CAA section 202(a)(1) was not designed with such a problem in mind. The inability of the EPA's GHG emission standards to materially impact the identified risks both corroborates the interpretation of CAA section 202(a)(1) adopted in this final action and serves as an independent basis to revoke those standards, separate and apart from the question of statutory interpretation and of the nature of the EPA's authority under this provision.

The remainder of this section describes the need for regulatory action and the scope of this final action, the repeal of new motor vehicle and engine GHG emission standards for MYs 2012 to 2032 and beyond, and minor conforming adjustments to unrelated emission standards for new motor vehicles and engines that we are not altering as part of this rulemaking. We acknowledge that the EPA's decision to regulate new motor vehicle and engine GHG emissions has caused significant expenditure of resources by, and an imposition of burdens on, Federal, State, local, and private-sector entities, and consider those interests to the extent possible consistent with limits on our statutory authority. These interests emphasize the need for urgent action to avoid further expenditures in reliance on an unlawful regulatory framework that does not further public health or welfare in any material respect relevant to the global climate change concerns identified and relied upon in the 2009 Endangerment Finding.

Section III of this preamble sets out relevant background, including the EPA's prior positions on regulating GHGs, the Supreme Court's decision in Massachusetts, the EPA's response in the 2008 ANPRM and events leading up to the Endangerment Finding, the approach taken in the Endangerment Finding, and the regulations issued by the EPA since 2009 as a result of the Endangerment Finding. We also summarize the premises, assumptions, and conclusions in the Endangerment Finding and the developments since 2009 that led the Administrator to develop concerns sufficient to initiate reconsideration of the ongoing validity and reliability of the Endangerment Finding in early 2025.

Section IV of this preamble describes our legal authority to rescind the Endangerment Finding and repeal the resulting GHG emission standards issued under CAA section 202(a)(1). Because this final action does not impact fuel economy standards or emission standards for criteria pollutants and hazardous air pollutants regulated under the CAA, we explain the relationship between these regulations to set the outer bounds of the amendments at issue in this rulemaking. We summarize comments received on our authority for this final action, which largely acknowledged that the EPA may reconsider the prior actions covered by this rulemaking provided that we offer an adequate basis for the rescission and repeals, along with our responses to these comments.

Section V.A of this preamble finalizes the rescission and repeals of these prior actions on the basis that the Endangerment Finding exceeded our statutory authority under CAA section 202(a)(1). First, we conclude that the term “air pollution” as used in CAA section 202(a)(1) is best read in context as pollution that threatens health or welfare through local or regional exposure, consistent with the ordinary meaning of the term at the time of enactment, the statute's structure and history, and the EPA's longstanding practice before 2009. Second, we conclude that CAA section 202(a)(1) does not grant the Administrator “procedural discretion” to issue standalone findings that trigger a duty to regulate without analyzing and promulgating the required emission standards, or, conversely, to prescribe standards without making the requisite findings for the air pollutant emissions and class or classes of new motor vehicles or engines at issue. Third, we conclude that CAA section 202(a)(1) does not authorize the Administrator to sever the finding of endangerment from the finding of causation or contribution such that there is no nexus between the emissions at issue and the identified dangers to public health or welfare. Rather, CAA section 202(a)(1) requires the Administrator to find that the relevant air pollutant emissions from the class or classes of new motor vehicles or engines at issue cause, or contribute to, the same air pollution that the Administrator finds endangers public health or welfare, without relying on international emissions not covered by the statute. As the Supreme Court made clear in Loper Bright, we can no longer rely on statutory silence or ambiguity to expand our regulatory power. We also explain that the EPA reached contrary conclusions in the Endangerment Finding by redefining key statutory terms and misconstruing the Supreme Court's decision in Massachusetts, which, even on its own terms, did not purport to require the Agency to launch a GHG regulatory program under CAA section 202(a)(1). We briefly summarize the public comments received for and against this interpretation, including with respect to the meaning of “air pollution” in context and the scope of Massachusetts, as well as our general responses to these comments.

Section V.B of this preamble finalizes the rescission and repeals on the additional basis that the Nation's potential response to global climate change concerns is an issue that has significant economic and policy impacts, including to Americans' basic way of life, that Congress did not clearly authorize the EPA to decide by invoking authority to prescribe emission standards under CAA section 202(a)(1). We conclude, consistent with West Virginia, UARG, and other relevant precedents, that the Nation's policy response to global climate change concerns is a question for Congress to decide in the first instance. Because nothing in the statute clearly authorizes the Administrator to assert the power to resolve this major question by prescribing emission standards, let alone by mandating a shift toward EVs, we conclude that CAA section 202(a)(1) does not authorize the Endangerment Finding or subsequent regulations. We briefly summarize public comments received for and against this invocation of the major questions doctrine, including the assertion by some commenters that Massachusetts shields CAA section 202(a)(1) from this analysis, and our general responses to these comments.

Section V.C of this preamble sets out the robust public response to our request for comments on the efficacy of new motor vehicle and engine GHG emission standards in addressing the global climate change concerns animating the Endangerment Finding and subsequent regulations. We summarize the climate impact modeling submitted by commenters and the updated modeling we performed to evaluate the competing data and conclusions received. As explained below, we conclude that even the complete elimination of all GHG emissions from all new and existing LD, MD, and HD vehicles in the U.S. would not alter predicted trends in global mean surface temperature (GMST) \5\ or global mean sea level rise (GSLR) \6\ beyond de minimis levels that are below the accepted variability in GMST and GSLR measurement. Assuming for purposes of this final action the validity and the uncertainties inherent in the relevant models, the EPA estimates that the elimination of all U.S. vehicle and engine GHG emissions would result in an approximately 0.013 degree Celsius ([deg]C) difference in GMST increase by 2050 compared to the baseline and an approximately 0.037 [deg]C difference by 2100 compared to the baseline. Using similar methods, we estimate that this scenario would result in an approximately 0.09-centimeter (cm) difference in GSLR by 2050 compared to the baseline and an approximately 1.40 cm difference by 2100 compared to the baseline. For context, variability in GMST measurement from 2016 to 2025 was 0.14 [deg]C, which is almost four times greater than the modeled GMST impact by 2100 of eliminating all U.S. vehicle and engine GHG emissions.\7\

\5\ As GMST is a widely used metric for tracking temperature changes related to global climate change concerns, we use the term interchangeably with “global temperature” within this preamble and supporting documentation.

\6\ As GSLR is a widely used metric for tracking sea level rise related to global climate change concerns, we use the term interchangeably with “global sea level,” “sea level,” and “sea level rise” within this preamble and supporting documentation.

\7\ NOAA National Centers for Environmental Information, Climate at a Glance: Global Time Series, NOAAGlobalTemp, (Jan. 2026) available at https://ncei.noaa.gov/access/monitoring/climate-at-a-glance/global/time-series/globe/land_ocean/tavg/ytd/12/1950-2025.

Importantly, this scenario is a dramatic overestimation of the potential impacts of GHG emission standards, which apply only to new vehicles and engines and do not eliminate emissions from existing vehicles. Taking this reality into account, the anticipated impact of GHG emission standards under CAA section 202(a)(1) is a further fraction of the modeled impacts of eliminating all U.S. vehicle and engine GHG emissions. Under an illustrative scenario in which the modeled impacts are discounted by 50 percent, which generally reflects the emission reductions requirements of the EPA's most recent 2024 LD and MD Multi-Pollutant Emission Standards Rule and 2024 HD GHG Emission Standards Rule (together, 2024 GHG Emission Standards Rules) that further restricted GHG emissions from MY 2027 levels for MY 2032 and beyond, we estimate an approximately 0.007 [deg]C difference in GMST increase by 2050 and 0.019 [deg]C by 2100 and an approximately 0.005 cm difference in GSLR by 2050 and 0.7 cm by 2100, all of which amount to one percent or less of the total projected change from the baseline. We conclude that these impacts are de minimis and that the futility of GHG emission standards under CAA section 202(a)(1) further supports the understanding that Congress did not design that provision to authorize or require the Administrator to prescribe standards in response to global climate change concerns. In addition, we conclude that the futility of the GHG emission standards renders maintaining such regulations unreasonable, separate and apart from the validity of the Endangerment Finding, because the enormous costs imposed do not materially further public health or welfare. Under any legal standard, it is unreasonable for the EPA to impose trillions of dollars in costs on manufacturers and American consumers in exchange for results that do not materially further congressional objectives--at least absent an extraordinarily clear indication in the statutory text. We briefly summarize public comments received on these aspects of the proposal and set out our general responses, including the assertion by some commenters that Massachusetts requires EPA to ignore the practical effect of its regulations when making findings under CAA section 202(a)(1) and when promulgating the regulations required by such findings.

Section VI of this preamble describes the additional bases in the proposal that we are not finalizing in this action, including the alternative basis in section IV.B of the preamble to the proposed rule that the Administrator exercise discretion under CAA section 202(a)(1) to rescind the Endangerment Finding and repeal associated regulations by making a superseding finding. We received comments in support of this alternative basis, including from commenters asserting that the EPA compiled and analyzed the scientific record unreasonably in 2009 by severing the analysis of endangerment and contribution and issuing findings separately from emission standards and from commenters asserting that the scientific record did not then, or does not now, provide the certainty necessary to make such findings. We also received comments in opposition to this alternative basis, including from commenters asserting that the scientific record supporting the findings is “overwhelming” and has been strengthened in the intervening years. Although the Administrator continues to harbor concerns regarding many of the scientific inputs and analyses underlying the Endangerment Finding, we are not finalizing this alternative given our conclusion that the EPA lacks statutory authority to regulate in response to global climate change concerns under CAA section 202(a)(1). The legal interpretation finalized in this action means that we cannot resolve remaining scientific controversies in this regulatory context and renders it unnecessary and inappropriate to invoke the Administrator's authority to exercise judgment on these questions under that provision.\8\ Furthermore, we explain that we are not finalizing several of the additional bases for repealing GHG emission standards set out in section V of the preamble to the proposed rule, which are similarly unnecessary given the predicate conclusion on the scope of our authority under CAA section 202(a)(1). We briefly summarize the input received on these alternatives in the interests of transparency and public engagement but are not responding to comments on these specific issues, which are outside the scope of the bases for this final action.

\8\ For similar reasons, and in light of concerns raised by some commenters about the draft report authored by the U.S. Department of Energy's Climate Working Group (CWG), the EPA is not relying on the May 27, 2025 CWG draft report entitled “Impact of Carbon Dioxide Emissions on the U.S. Climate” or the July 23, 2025 CWG report entitled “A Critical Review of Impacts of Greenhouse Gas Emissions on the U.S. Climate” for any aspect of this final action.

Section VIII of this preamble details the scope of the repeals, including its relationship to distinct regulatory programs and Federal preemption, the revisions to 40 CFR parts 85, 86, 600, 1036, 1037, and 1039 required to effectuate repeal of all new motor vehicle and engine GHG emission standards, and conforming adjustments to regulatory provisions that we did not reopen or propose to substantively revise. Specifically, we are not changing

elements of the regulations that are necessary for programs unrelated to the GHG emission standards, including emission standards for criteria pollutants, emission standards for hazardous air pollutants, or regulatory provisions related to the EPA's statutory role in vehicle fuel-economy standards administered by the National Highway Traffic Safety Administration (NHTSA).

As explained in detail below, the conclusions presented in sections V.A, V.B, and V.C of this preamble provide independent grounds for rescinding the 2009 Endangerment Finding and repealing the GHG emission standards. Moreover, the conclusions in section V.A of this preamble-- that “air pollution” as used in CAA section 202(a)(1) is best read as pollution that threatens public health or welfare through local or regional exposure; that the Administrator cannot trigger the duty to regulate without analyzing and promulgating standards; and that the finding of endangerment cannot be severed from the finding of causation of contribution--are all also independent conclusions that stand on their own. Each basis for this final action presented in section V of this preamble is severable, and each basis alone provides sufficient justification to rescind the Endangerment Finding and repeal the GHG emission standards for new motor vehicles and engines. If any basis is determined in the course of judicial review to be invalid, that partial invalidation will not affect the other bases, and the EPA intends the remainder of this final action stand on the remaining basis or bases.

This preamble includes an overview of the EPA's rationale, including several technical documents developed in support of this final action, as well as summaries of comments received during the public hearing on the proposal, additional consultation and listening sessions, and via the rulemaking docket. For a full summary of comments received and our complete responses thereto, please see the “Response to Comments” document available in the docket for this rulemaking.\9\ The final Regulatory Impact Analysis (RIA) for this rulemaking, on which we did not rely for any aspect of this final action, is also available in the docket for this rulemaking.\10\

\9\ “Rescission of the Greenhouse Gas Endangerment Finding and Motor Vehicle Greenhouse Gas Emission Standards Under the Clean Air Act: Response to Comments.” EPA 420-R-26-003. February 2026.

\10\ “Rescission of the Greenhouse Gas Endangerment Finding and Motor Vehicle Greenhouse Gas Emission Standards Under the Clean Air Act: Regulatory Impact Analysis.” EPA-420-R-26-002. February 2026.

Immediately upon taking office in 2025, President Trump established as the policy of the United States new Executive Branch priorities for energy, transportation, and consumer choice and committed agencies to ensuring regulations remain within constitutional and statutory bounds. On January 20, 2025, the President issued E.O. 14154, entitled “Unleashing American Energy,” to address the burdens placed by unnecessary regulations on energy affordability, job creation, and national security.\11\ The President directed the Administrator to submit recommendations to the Director of the Office of Management and Budget (OMB) on the legality and continuing applicability of the 2009 Endangerment Finding.\12\ On February 19, 2025, the President issued E.O. 14219, entitled “Ensuring Lawful Governance and Implementing the President's `Department of Government Efficiency' Deregulatory Initiative,” which further instructed agencies, including the EPA, to review existing regulations for consistency with the Constitution and the best reading of the authorizing statute.\13\

\11\ Executive Order 14154, 90 FR 8353 (Jan. 29, 2025).

\12\ Id. section 6(f).

\13\ Executive Order 14219, 90 FR 10583 (Feb. 25, 2025).

Upon confirmation by the Senate, Administrator Lee Zeldin committed the EPA to prioritizing its core statutory missions and ensuring that all regulatory actions are clearly grounded in statutory authority and the best reading of the law. As part of these efforts, and consistent with E.O. 14154, the Administrator initiated a review of the legality and applicability of the Endangerment Finding. On February 19, 2025, the Administrator submitted a memorandum to the OMB Director recommending that the EPA reconsider the Endangerment Finding to address legal and scientific developments that appeared to undermine the bases for that action and subsequent regulations.\14\ The Administrator noted that recent Supreme Court decisions, including Loper Bright, West Virginia, UARG, and Michigan v. EPA, 576 U.S. 743 (2015), provided further instruction as to how we should interpret and apply the statutes Congress entrusted us to administer.\15\ The Administrator further noted that the Endangerment Finding recognized significant uncertainties in its conclusions and assumptions that should be evaluated in light of more recent empirical data and scientific evidence.\16\ Accordingly, the Administrator announced on March 12, 2025, that the EPA would reconsider the Endangerment Finding and subsequent actions to determine whether our GHG regulations have an adequate statutory basis and to seek public input on developments since 2009.\17\

\14\ Memorandum from Lee Zeldin, Administrator, U.S. Environmental Protection Agency, to Russell Vought, Director, Office of Management and Budget (Feb. 19, 2025) (Feb. 19, 2025 Memo), available in the docket for this rulemaking.

\15\ Id. at 1.

\16\ Id. at 8.

\17\ “Trump EPA Kicks Off Formal Reconsideration of Endangerment Finding with Agency Partners” (Mar. 12, 2025), available at https://www.epa.gov/newsreleases/trump-epa-kicks-formal-reconsideration-endangerment-finding-agency-partners.

On July 29, 2025, the Administrator signed a proposed rule setting out the results of the EPA's reconsideration to date and proposing to rescind the Endangerment Finding and repeal all GHG emission standards for LD, MD, and HD new motor vehicles and engines promulgated since 2009 under CAA section 202(a)(1). “Reconsideration of 2009 Endangerment Finding and Greenhouse Gas Vehicle Standards,” 90 FR 36288 (Aug. 1, 2025). We proposed that the term “air pollution” in CAA section 202(a)(1) is best read in context as referring to pollution that threatens public welfare through local or regional exposure, consistent with historical practice and principles of proximate cause, such that the EPA's regulatory authority does not extend to global climate change concerns. Relatedly, we proposed that the major questions doctrine applies to the question whether the EPA may decide the Nation's policy response to global climate change concerns and that Congress did not clearly delegate that decision when it authorized the Agency to prescribe emission standards for new motor vehicles and engines. We also proposed that the Endangerment Finding departed from the statute in additional ways by asserting “procedural discretion” to issue findings separately from the required standards and severing the question whether GHG emissions from motor vehicles and engines contribute to increases in global GHG concentrations from the question whether cumulative global GHG concentrations endanger public health and welfare.

In the alternative, we proposed that the Administrator exercise discretion under CAA section 202(a)(1) to issue a new finding that the conclusions reached in the Endangerment Finding

are not supported by the scientific record, including because the EPA unreasonably compiled and analyzed the record in 2009 and because intervening developments have cast significant doubt on the Endangerment Finding's core premises and assumptions. For example, we proposed that data from 2009-2024 demonstrate that many of the predictive analyses relied upon in the Endangerment Finding were overly pessimistic and underestimated the ability of natural processes to compensate for the identified trends.

Finally, we proposed three alternative bases to repeal the GHG emission standards separate and apart from the proposed rescission of the Endangerment Finding. First, we proposed that there is no “requisite technology,” as required for emission standards to go into effect under CAA section 202(a)(2), that is capable of having a measurable impact on the global climate change concerns that were the basis of the Endangerment Finding. Second, we proposed that the Agency's GHG regulatory program is futile because emissions from covered vehicles have a de minimis impact on global climate change concerns and that this consideration bears on the proper interpretation and implementation of CAA section 202(a)(1). Third, we proposed that the GHG emission standards harm public health and welfare on balance by increasing prices and decreasing consumer choice, thereby slowing the replacement of older vehicles that are less safe and emit a greater volume and variety of air pollutants. We sought comment on these and additional issues throughout the proposal, including the EPA's authority to reconsider and rescind the Endangerment Finding, relevant data and information bearing on the efficacy of the GHG emission standards, and any additional reasons we should consider for repealing or retaining the Endangerment Finding and associated regulations.

This final action is informed by the significant public input received from a diverse array of stakeholders since publication of the proposal in the Federal Register on August 1, 2025. The EPA extended the original comment deadline of September 15, 2025, to September 22, 2025.\18\ To facilitate participation, we held four days of virtual public hearings on August 19 through August 22, 2025, during which we heard oral testimony from more than 600 speakers. Consistent with the EPA's Tribal Consultation Policy, we also invited all federally recognized Tribes to participate in consultation, which resulted in four consultation sessions in addition to oral testimony and written submissions from several federally recognized Tribes and tribal organizations. For more information on public participation, see the public hearing, tribal consultation, and meeting summaries available in the docket for this rulemaking.

\18\ 90 FR 39345 (Aug. 15, 2025).

The EPA received approximately 572,000 written comments from more than 31,000 unique entities and 169 mass letter writing campaigns during the public comment period, including written submissions received in connection with the public hearing and Tribal consultation sessions. The EPA considered all input received during the public comment period in evaluating this final action, and all written comments, as well as a transcript of the public hearing, are available in the docket for this rulemaking.\19\ Given the significant volume of comments received, this preamble includes summaries of relevant comments in the appropriate subsection, along with summaries of the EPA's responses. For more detailed descriptions of comments received and our responses, see the Response to Comments document available in the docket for this rulemaking.\20\

\19\ See 42 U.S.C. 7607(d)(1)(C), (d)(4)(B)(i), (d)(5)-(6). Note that although all public comments are posted in the docket, the EPA has not considered or responded separately to comments received after the close of the comment period on September 22, 2025.

\20\ “Rescission of the Greenhouse Gas Endangerment Finding and Motor Vehicle Greenhouse Gas Emission Standards Under the Clean Air Act: Response to Comments.” EPA 420-R-26-003. February 2026.

The EPA received comments on rulemaking process, including with respect to the length of the comment period and the content of the proposed rule. The EPA notes that most commenters did not raise concerns with these aspects of the rulemaking process and believes that the large volume of comments received and extensive participation in the public hearing demonstrate that interested stakeholders were able to submit views, data, and information for consideration. Below, we summarize comments received on the rulemaking process along with our responses.

Comment: Many commenters appreciated the chance to weigh in on the underlying science relevant to the Endangerment Finding and regulations under CAA section 202(a)(1) for the first time since 2009 and asserted that the rulemaking process allowed ample public participation and was consistent with statutory requirements.

Response: The EPA appreciates and agrees with these comments. As discussed in the proposed rule, we believe that public participation on regulatory issues of this magnitude is essential to good government. Because we are not finalizing many of the alternative bases for the proposed rescission and repeals, this final action does not resolve or substantively respond in full to issues raised in public comments that are outside the scope of the bases finalized in this action. We look forward to further engagement on these additional topics in the future. For further discussion of the alternative bases we are not finalizing, please see section VI of this preamble and the Response to Comments document.

Comment: Other commenters argued that we should have provided a longer comment period, including a comment period of up to six months, given the scope of this rulemaking and significant public interest in the underlying issues. Some of these commenters suggested that the statute requires providing a “reasonable” period for public comment. Others pointed to language in E.O. 12866 providing that “a meaningful opportunity to comment on any proposed regulation . . . should include a comment period of not less than 60 days.”

Response: The EPA disagrees with these comments. The significant volume of comments received during the comment period, as well as the number of participants in the four-day public hearing, demonstrate that the interested public had a reasonable opportunity to participate in this rulemaking by engaging with the EPA. The public comment period fully satisfied the CAA's detailed requirements for public participation. For example, CAA section 307(d)(5) requires that the Administrator allow “thirty days after completion of the [public hearing] to provide an opportunity for submission of rebuttal and supplementary information,” \21\ and CAA section 307(h) states the intent of Congress that the Administrator “ensure a reasonable period for public participation of at least 30 days.” \22\ With respect to E.O. 12866, we note that the language cited generally tracks the less detailed rulemaking provisions of the

Administrative Procedure Act (APA) rather than the specific processes Congress established as applicable to this rulemaking in CAA section 307(d), and is intended as non-binding, general guidance for agency rulemakings that yields to more specific statutes and circumstances.\23\

\21\ See 42 U.S.C. 7607(d)(5).

\22\ See 42 U.S.C. 7607(h).

\23\ See 58 FR 51735, 51740 (Oct. 4, 1993) (providing that “each agency should afford the public a meaningful opportunity to comment on any proposed regulation, which in most cases should include a comment period of not less than 60 days”) (emphases added).

Comment: Some commenters asserted that the proposed rule was procedurally flawed under CAA section 307(d)(3) for various reasons, including the assertion that we should have directly referenced, summarized, and included in the docket pertinent findings by the National Academy of Sciences (NAS). These commenters asserted that we should repropose with additional discussion of NAS materials, which, they assert, are central to the rulemaking.

Response: The EPA disagrees that the proposal was procedurally flawed in any manner that impacts this final action. The statement of basis and purpose included in the proposal satisfied the requirements of CAA section 307(d)(3)(A)-(C) by including not only the factual data, methodology, and major legal interpretations and policy considerations relevant to the proposal, but also a detailed discussion of relevant factual and legal developments since 2009 impacting the EPA's reconsideration.\24\ With respect to the NAS, the statute references only “pertinent findings, recommendations, and comments” by the NAS and discussion of differences from the proposal only when it “differs in any important respect.” \25\ In section IV.B of the preamble to the proposed rule, we explained that the Administrator had considered the most recently available scientific information, including assessments by the U.S. Global Change Research Program (USGCRP) and United Nations Intergovernmental Panel on Climate Change (IPCC). With respect to discussion of global climate change concerns, the NAS findings cited by these commenters or in previous EPA rulemakings rely upon, and are duplicative of, these assessments.\26\ In other respects, the NAS findings deal with matters that were not pertinent to the substance of the proposal, including particular emissions-reduction technologies,\27\ matters pertaining to criteria pollutant standards,\28\ and how to utilize Social Cost of Carbon (SCC) methodologies in an RIA or similar analysis.\29\

\24\ 42 U.S.C. 7607(d)(3)(A)-(C).

\25\ 42 U.S.C. 7607(d)(3).

\26\ See, e.g., 88 FR 29184, 29208, 29394 (May 5, 2023) (proposed HD GHG emission standards) (briefly citing NAS findings together with USGCRP and IPCC reports). To the extent commenters cited or intended to reference the September 2025 report developed, published, and submitted by the NAS during the comment period for the purposes of informing this rulemaking, we note that the Administrator could not have considered the September 2025 report when signing the proposal in July 2025.

\27\ See, e.g., 88 FR 29284-86 (discussing NAS findings on challenges and advantages associated with particular technologies for reducing vehicle emissions). The EPA notes that none of the bases finalized in this action, including the futility basis discussed in section V of this preamble, turn on the relative advantages of particular technologies in reducing GHG emissions from vehicles and engines. Rather, we are finalizing that GHG emission standards under CAA section 202(a)(1) do not have more than a de minimis impact on the health and welfare dangers identified in the Endangerment Finding because even the complete elimination of GHG emissions from new and existing LD, MD, and HD vehicles would not materially impact GMST or GSLR as a proxy for adverse impacts to public health and welfare.

\28\ See, e.g., 88 FR 29224 (discussing NAS materials related to particulate matter, ozone, NOX, sulfur oxides (SOX), and hazardous air pollutants). As noted at proposal, the EPA is not addressing criteria emission standards in this rulemaking, and incidental co-benefits of GHG emission standards are not pertinent to the legal bases on which we are relying in this final action.

\29\ See, e.g., 88 FR 29370-72 (discussing methodologies for estimating and utilizing SCC). As noted at proposal, the EPA has consistently viewed criticisms of the SCC methodology as out of scope because it played no role in the Endangerment Finding and is not relevant to the statutory standard for regulation under CAA section 202(a). Moreover, the U.S. Government is no longer using the SCC methodology for purposes of estimating costs and benefits.

In any event, commenters did not identify NAS materials pertinent to the bases on which we are relying in this final action. Whether CAA section 202(a)(1) authorizes the EPA to regulate in response to global climate change concerns by prescribing emission standards is a matter of statutory interpretation, not scientific analysis within the NAS's purview. As explained in section VI of this preamble, we are not finalizing the alternative proposal to base the rescission and repeals on a new finding by the Administrator under CAA section 202(a)(1). We note that the NAS developed and submitted during the public comment period for this rulemaking a new report responding to the concerns underlying the alternative proposal.\30\ This submission and additional NAS materials regarding the science of climate change are not pertinent to the bases for this final action, which are legal in nature and rest on statutory interpretation, application of judicial precedent, and legal conclusions drawn from modeling generally accepted for purposes of predicting impacts within the causal framework endorsed by the Endangerment Finding. As discussed in section V.C of this preamble, the NAS has expressed approval for and encouraged the development of the underlying models the EPA is using in this action to evaluate comments received on futility and reach conclusions about the impact of futility on the legality of the Endangerment Finding and associated GHG emission standards.

\30\ See Comment ID EPA-HQ-OAR-2025-0194-0756, NAS 2025, “Effects of Human-Caused Greenhouse Gas Emissions on U.S. Climate, Health, and Welfare.” Washington, DC: The National Academies Press.

Comment: Additionally, some commenters asserted that the proposed rule should have been made available to the Science Advisory Board (SAB) before publication. These commenters asserted that SAB input is centrally relevant to the rulemaking but generally acknowledged that the EPA did not submit the Endangerment Finding or subsequent reconsideration denials in 2010 and 2022 to the SAB for prior review.

Response: By statute, the Administrator is to make available to the SAB “any proposed criteria document, standard, limitation, or regulation” when such material “is provided to any other Federal agency for formal review and comment.” \31\ The proposal for this rulemaking, which sought comment on rescinding the Endangerment Finding and related GHG emission standards, was not a “criteria document, standard, limitation, or regulation” that would impose obligations on the EPA or any regulated entities if finalized. We note that the EPA used the same interpretation to propose and finalize the Endangerment Finding, as well as issue the 2010 and 2022 denials of petitions for reconsideration, without prior SAB review. Whereas those actions obligated and maintained the obligation for the EPA to issue GHG emission standards that are subject to SAB review, the actions contemplated in the proposal would relieve the Agency of the obligation to maintain and issue regulations with SAB input as well as ongoing obligations for regulated parties. Nor did we submit the proposal to “any other Federal agency for formal review and comment.” The EPA has previously taken the position that “formal” consultation is not required for CAA section 202(a)(1) actions and that informal interagency review as part of the non-statutory E.O. 12866 process is

not encompassed within the statutory term “formal review and comment.” \32\

\31\ 42 U.S.C. 4365(c)(1).

\32\ See Resp. Br. 75-79, Delta Constr. Co. v. EPA, No. 11-1428 (filed Nov. 24, 2014); Coal. for Responsible Regulation, Inc. v. EPA, 684 F.3d 102, 124 (D.C. Cir. 2012), reversed in part in UARG, 573 U.S. 302 (noting “it is not clear that EPA provided the Endangerment Finding” to any other agency and that petitioners failed to respond to the argument).

Given the nature of the proposal and the legal bases on which the EPA relies in this final action, the possibility of SAB review is not material to the outcome of this rulemaking. Because we conclude that CAA section 202(a)(1) does not authorize the EPA to regulate in response to global climate change concerns, this final action does not turn on scientific findings made with respect to the validity, certainty, or extent of global climate change. We note that the D.C. Circuit has previously determined that failing to secure SAB review of the Endangerment Finding was not “of such central relevance” that there is a “substantial likelihood” the action “would have been significantly changed” absent such failure.\33\ Commenters provided no reason to conclude that SAB review of this rulemaking to rescind the Endangerment Finding would be of central relevance for the first time, particularly given the ample recommendations already provided on previously promulgated GHG emission standards and the legal nature of the rationales being finalized.

\33\ Coal. for Responsible Regulation, 684 F.3d at 124 (quoting 42 U.S.C. 7607(d)(8)); see also Am. Petrol. Inst. v. Costle, 665 F.2d 1176, 1188-89 (D.C. Cir. 1981) (similar with respect to ozone standard not submitted for SAB review).

Comment: Finally, commenters offered competing positions on the EPA's proposal to rescind the 2022 and 2010 denials of petitions for reconsideration entitled “Endangerment and Cause or Contribute Findings for Greenhouse Gases Under Section 202(a) of the Clean Air Act; Final Action on Petitions,” 87 FR 25412 (Apr. 29, 2022), and “EPA's Denial of the Petitions to Reconsider the Endangerment and Cause or Contribute Finding for Greenhouse Gases Under Section 202(a) of the Clean Air Act,” 75 FR 49556 (Aug. 13, 2010).\34\ Supportive commenters argued that the 2022 and 2010 petitions raised a variety of valid procedural, legal, scientific, and transparency-related issues with the Endangerment Finding. Conversely, adverse commenters asserted that the EPA erred in proposing to rescind the petition denials at the same time as proposing to rescind the Endangerment Finding, which was the subject of the petitions for reconsideration. These commenters argued that we lack authority to rescind a petition denial and provided insufficient rationale in the proposal to support such a rescission.

\34\ As noted at proposal, the 2022 petition denials included a notice of decision in the Federal Register, brief letters communicating the denials to the petitioners, and a decision document entitled “EPA's Denial of Petitions Relating to the Endangerment and Cause or Contribute Findings for Greenhouse Gases Under Section 202(a) of the Clean Air Act” (Apr. 21, 2022) (“2022 Denials”), available online at https://www.epa.gov/system/files/documents/2022-04/decision_document.pdf.

Response: The EPA appreciates the comments received on this issue and is taking the opportunity to clarify that the 2022 and 2010 reconsideration petition denials no longer represent the Agency's views and should not be relied upon for any statements inconsistent with this final action. As explained at proposal, the petition denials already had no prospective legal effect and were not binding on the EPA or interested parties. We proposed to rescind the petition denials along with the Endangerment Finding and associated GHG emission standards to promote consistency and avoid confusion, as the petition denials relied in large part on the prior positions in those actions that we proposed to abandon. In this final action, we are repudiating the EPA's positions since 2009 to the extent and for the reasons set out in section V of this preamble. We are also finalizing rescission of the petition denials because those decisions affirmed the same legal positions and, moreover, decided scientific questions that are unnecessary and inappropriate for the Agency to address under CAA section 202(a)(1). For discussion of the EPA's authority to reconsider prior actions unless provided otherwise by the governing statute, see section IV of this preamble. 2. Updates From the Proposal in This Final Action

The EPA received supportive and adverse comments on virtually all substantive aspects of the proposal from a wide variety of stakeholders, including vehicle and engine manufacturers and suppliers, nearly all 50 States and the District of Columbia, elected representatives at the local, State, and Federal levels (including many members of the U.S House of Representatives and the U.S. Senate), consumer and labor groups, EV advocates, manufacturers, and suppliers, educational institutions, environmental groups, and individual citizens. With respect to the primary basis for the proposed repeal, we received detailed comments offering legal arguments for and against our proposed interpretation of the statute and the applicability and impact of the major questions doctrine. With respect to the alternative bases for the proposed repeal, we received extensive data, models, and arguments on virtually every aspect of climate science and climate impacts discussed at proposal. Submissions related to the alternative climate science basis for rescission and repeal in section IV.B of the preamble to the proposed rule constituted the largest share of public comments received. Commenters also submitted substantial information in response to our request for comment on the alternative rationales in section V of the preamble to the proposed rule, including data and modeling addressing the historical and potential impacts of GHG emission standards under CAA section 202(a)(1) on the global climate change concerns animating the Endangerment Finding, such as trends in GMST and GSLR.

The EPA is finalizing the primary basis for the rescission and repeals as proposed for the reasons stated in section V of this preamble. We conclude that the best reading of the statute does not authorize the EPA to prescribe GHG emission standards based on global climate change concerns and, moreover, that EPA erred in issuing the Endangerment Finding as a standalone action that severed the consideration of endangerment from the consideration of contribution and failed to engage with the standards that must issue when making such a finding. We further conclude, as proposed, that the major questions doctrine applies and bars the EPA from asserting the authority to decide the Nation's policy response to global climate change concerns, including by attempting to force a shift to EVs, based on language authorizing the Agency to prescribe emission standards. Finally, we conclude that the inability of GHG emission standards under CAA section 202(a)(1) to measurably impact the global climate change concerns identified in the Endangerment Finding further supports our interpretation of the statute and provides an additional reason to repeal the GHG emission standards.

In light of these conclusions, and as discussed further in section VI of this preamble, the EPA is not finalizing the alternative proposed bases for rescission and repeal. The robust public response to the alternative climate science basis revealed ongoing disagreement among commenters with respect to aspects of the scientific analysis underpinning the Endangerment Finding, including the certainty of the causal chain, the extent of endangerment attributable to U.S. new motor vehicle and engine

emissions, the countervailing domestic benefits of global climate change, and the capacity of natural and human systems to adapt and mitigate potential adverse impacts and the relevance of such topics to the analysis. However, we conclude that the EPA lacks statutory authority to regulate GHG emissions from new motor vehicles and engines in the first instance under CAA section 202(a)(1). Accordingly, although the Administrator continues to harbor concerns regarding the scientific determinations underlying the 2009 Endangerment Finding, we cannot resolve these questions under our regulatory authority in CAA section 202(a)(1), and comments received on these subjects are outside the scope of this final action. Similarly, the EPA's lack of authority to regulate GHG emissions from new motor vehicles and engines places comments on the alternative bases for repealing the standards-- including the “requisite technology” requirement in CAA section 202(a)(2) and additional factors relative to standards-setting--outside the scope of this final action.

This final action removes all existing regulations that require new motor vehicle and engine manufacturers to measure, report, or comply with GHG emission standards. Specifically, the EPA is removing regulations in 40 CFR parts 85, 86, 600, 1036, and 1037 pertaining to the control of GHG emissions from LD, MD, and HD new motor vehicles and engines, including emission standards; test procedures; averaging, banking, and trading (ABT) requirements; reporting requirements; and fleet-average emission requirements.\35\ As a result of these changes, motor vehicle and engine manufacturers no longer have future or current obligations for the measurement, control, or reporting of GHG emissions for any vehicle or engine, including for previously manufactured MYs. However, we did not reopen or modify any regulations necessary for criteria pollutant and air toxic measurement and standards, Corporate Average Fuel Economy (CAFE) testing, and associated fuel economy labeling requirements.

\35\ “Light-Duty Vehicle Greenhouse Gas Emission Standards and Corporate Average Fuel Economy Standards,” 75 FR 25324 (May 7, 2010); “Greenhouse Gas Emissions Standards and Fuel Efficiency Standards for Medium- and Heavy-Duty Engines and Vehicles,” 76 FR 57106 (Sept. 15, 2011); “2017 and Later Model Year Light-Duty Vehicle Greenhouse Gas Emissions and Corporate Average Fuel Economy Standards,” 77 FR 62624 (Oct. 15, 2012); “Greenhouse Gas Emissions and Fuel Efficiency Standards for Medium- and Heavy-Duty Engines and Vehicles-Phase 2,” 81 FR 73478 (Oct. 25, 2016); “The Safer Affordable Fuel-Efficient (SAFE) Vehicles Rule for Model Years 2021- 2026 Passenger Cars and Light Trucks,” 85 FR 24174 (Apr. 30, 2020); “Revised 2023 and Later Model Year Light-Duty Vehicle Greenhouse Gas Emissions Standards,” 86 FR 74434 (Dec. 30, 2021); “Multi- Pollutant Emissions Standards for Model Years 2027 and Later Light- Duty and Medium-Duty Vehicles,” 89 FR 27842 (Apr. 18, 2024) (2024 LD and MD Multi-Pollutant Emission Standards Rule); “Greenhouse Gas Emissions Standards for Heavy-Duty Vehicles-Phase 3,” 89 FR 29440 (Apr. 22, 2024) (2024 HD GHG Emission Standards Rule).

The EPA received comments from stakeholders related to the proposed revisions to the engine and vehicle GHG regulations. In general, we are finalizing the vast majority of the proposed regulatory changes for LD and MD engines and vehicles. For HD engines and vehicles, we are removing the GHG emission standards and related certification and compliance procedures, as proposed. However, in a change from the proposal, we are retaining the test procedures and compliance regulatory elements in the EPA regulations referenced by NHTSA in their regulatory program such that NHTSA can continue to implement its HD fuel efficiency program. Relevant comments and our responses are summarized in section VII of this preamble and the Response to Comments document accompanying this final action.

The EPA also received comments on our analyses included in the Draft Regulatory Impact Analysis (DRIA). A summary of these comments and the EPA's responses is included in the Response to Comments document accompanying this final action. The EPA made a number of updates to the analyses included in the final RIA, which is available in the docket for this rulemaking.

Congress originally enacted the language that became CAA section 202(a)(1) as part of the Motor Vehicle Pollution Control Act of 1965, which required the Secretary of Health, Education, and Welfare to “prescribe . . . standards, applicable to the emission of any kind of substance, from any class or classes of new motor vehicles or new motor vehicle engines, which in his judgment cause or contribute to, or are likely to cause or contribute to, air pollution which endangers the health or welfare of any persons.” \36\ Congress retained this language, while adding additional requirements for the content of emission standards, in the Air Quality Act of 1967,\37\ and, later, incorporated it into the Clean Air Act of 1970, which transferred the Secretary's regulatory authority to the newly created EPA and directed the Agency to issue standards that achieved significant reductions in certain criteria pollutants in the near-term.\38\ Separately, the 1970 CAA addressed emissions from existing vehicles and engines, stationary sources, and aircraft engines.\39\ In the following decades, Congress repeatedly amended CAA section 202 to specify particular regulatory goals and to require the EPA to regulate certain pollutants. Some of these provisions instructed the EPA to use CAA section 202(a)(1) in particular ways, while others separately directed the regulation of specified classes of vehicles or engines or specified air pollutants. As subsequently amended,\40\ CAA section 202 has remained a critical part of the comprehensive national framework for regulating air pollution, with Title II authorities for mobile sources working in tandem with the National Ambient Air Quality Standards (NAAQS) program and Title I authorities for stationary sources.\41\ Emission standards issued under CAA section 202 trigger requirements and enforcement mechanisms that can impose substantial liabilities on manufacturers and other regulated parties. Additional provisions in Title II prohibit selling, importing, or marketing vehicles and engines not in compliance with applicable emission standards, with violations subject to injunctive relief and significant monetary penalties.\42\

\36\ Public Law 89-272, section 202(a), 79 Stat. 992, 992-93 (1965).

\37\ Public Law 90-148, section 202(a), 81 Stat. 485, 499 (1967).

\38\ Public Law 91-604, 84 Stat. 1690 (1970).

\39\ Id.

\40\ In the CAA Amendments of 1977, Congress replaced the phrase “which endangers the public health or welfare” with “which may reasonably be anticipated to endanger public health or welfare.” Public Law 95-95, section 401(d)(1), 91 Stat. 685, 791 (1977); Public Law 101-549, section 203, 104 Stat. 2399, 2474 (1990).

\41\ See West Virginia, 597 U.S. at 707-11 (describing the relationship among the CAA's Title I programs).

\42\ 42 U.S.C. 7522-24. By regulation, the EPA has established a number of compliance and enforcement mechanisms specific to particular emission standards regimes, including GHG emission standards. For example, we have adopted a credit system whereby regulated parties that do not achieve the standards for a particular MY may carry forward a deficit for a certain number of years, provided that the entity overcomply in future years or purchase credits to make up for the prior shortfall. 40 CFR 86.1865-12.

In its first four decades administering the statute, the EPA invoked CAA section 202(a)(1) relatively infrequently and, in each case, to address local and regional air pollution problems through rulemakings that both prescribed

standards and set forth the Administrator's findings that the relevant air pollutant emissions cause, or contribute to, air pollution which may reasonably be anticipated to endanger public health or welfare.\43\ From 1965 to 2009, we invoked CAA section 202(a)(1) in at least fifteen final rules governing LD, MD, and HD vehicle and engine and motorcycle emissions of hydrocarbons (HC) and other volatile organic compounds (VOCs), carbon monoxide (CO), oxides of nitrogen (NOX), particulate matter (PM), and certain air toxics.\44\ Where possible, we relied in these final rules on more specific authorities provided elsewhere in CAA section 202, including subsections (a)(3)(B)-(D) for HD vehicles, (a)(3)(E) for motorcycles, and (l) for air toxics. Each of these regulations involved criteria pollutants or compounds that Congress expressly enumerated in CAA section 202 through iterative statutory amendments and addressed in additional provisions throughout the statute.\45\ We hewed closely to the vehicle and engine emission air pollution problems that Congress itself identified and did not use CAA section 202(a)(1) to expand into new regulatory arenas. As further explained in the following subsections, the EPA maintained this approach until 2009 and never invoked CAA section 202(a)(1) to regulate in response to global climate change concerns during this period.

\43\ See 74 FR 66501, 66527, 66538, 66543 (Dec. 15, 2009) (acknowledging this regulatory history).

\44\ See 72 FR 8428 (Feb. 26, 2007); 69 FR 2398 (Jan. 15, 2004); 66 FR 5002 (Jan. 18, 2001); 65 FR 59896 (Oct. 6, 2000); 65 FR 6698 (Feb. 10, 2000); 62 FR 54694 (Oct. 21, 1997); 62 FR 31192 (June 6, 1997); 60 FR 34326 (June 30, 1995); 60 FR 4712 (Jan. 24, 1995); 59 FR 48472 (Sept. 21, 1994); 59 FR 16262 (Apr. 6, 1994); 53 FR 43870 (Oct. 31, 1988); 49 FR 3010 (Jan. 24, 1984); 48 FR 48598 (Oct. 19, 1983); 45 FR 63734 (Sept. 25, 1980).

\45\ See Public Law 101-549, section 203, 104 Stat. 2399, 2474 (1990); Public Law 91-604, section 6, 84 Stat. 1676, 1690 (1970).

B. Petitions for Rulemaking and Massachusetts v. EPA

In October 1999, a coalition of 19 environmental organizations petitioned the EPA to regulate the emission of four GHGs-- CO2, methane, N2O, and HFCs--from new motor vehicles and engines under CAA section 202(a)(1). Petitioners claimed that these four GHGs were “air pollutant[s]” under CAA section 302(g), significantly contributed to global climate change, and met the statutory standard for regulation under CAA section 202(a)(1). Thus, petitioners claimed that the EPA had the authority and obligation to find that GHG emissions from new motor vehicles and engines cause, or contribute to, air pollution which may reasonably be anticipated to endanger public health or welfare and to prescribe standards in response.

In September 2003, after receiving and responding to nearly 50,000 public comments on the relevant issues, the EPA denied the 1999 petitions in a final action titled “Control of Emissions from New Highway Vehicles and Engines,” 68 FR 52922 (Sept. 8, 2003) (“2003 Denial”). The 2003 Denial asserted three primary reasons for denying the petitions. First, after “examin[ing] the fundamental issue of whether the CAA authorizes the imposition of control requirements” to “reduce the risk of global climate change,” we concluded that “CO2 and other GHGs cannot be considered `air pollutants' subject to the CAA's regulatory provisions for any contribution they may make to global climate change.” 68 FR 52925. Citing the Supreme Court's decision in FDA v. Brown & Williamson Tobacco Corp., 529 U.S. 120 (2000), we noted that the CAA does not address GHGs as a regulatory matter, including in then-recent amendments, and that the “EPA has used these provisions to address air pollution problems that occur primarily at ground level or near the surface of the earth.” 68 FR 52926. On this basis, we concluded that GHGs “are not air pollutants under the CAA's regulatory provisions, including sections 108, 109, 111, 112, and 202” because they categorically are not “air pollutant[s]” under the Act-wide definition in CAA section 302(g). 68 FR 52928. Second, we raised in the alternative several policy reasons for declining to regulate GHGs, including that regulating GHG emissions from motor vehicles and engines under the CAA would interfere with NHTSA's authority to implement fuel economy standards. 68 FR 52929. We also asserted that regulating GHG emissions from motor vehicle engines under the CAA would undermine then-President Bush's policy approach of addressing global climate change concerns comprehensively through voluntary actions and incentives, the promotion of research and technologies, and international negotiations. 68 FR 52930-31. That is, we reasoned that establishing GHG emission standards through unilateral action would “result in an inefficient, piecemeal approach to addressing the climate change issue” because “all significant sources and sinks of GHG emissions” should be considered in deciding the best way to achieve emissions reductions. 68 FR 52931.

In Massachusetts, the Supreme Court narrowly reversed the D.C. Circuit's decision upholding the EPA's denial of the 1999 petitions for rulemaking.\46\ The Court took particular issue with the EPA's reading of the Act-wide definition in CAA section 302(g), ruling that “[t]he Clean Air Act's sweeping definition of `air pollutant' . . . embraces all airborne compounds of whatever stripe” and provided no textual basis for excluding CO2 or the three other GHGs raised in the petitions for rulemaking. 549 U.S. at 528-29. The Court also addressed the EPA's reliance on Brown & Williamson, which the majority construed as having found no congressional intent to ban the sale of tobacco products outright because such an application of the relevant statute would have been highly unlikely and because the Food and Drug Administration (FDA) had expressly refused to assert such authority in the past. Id. at 530-31. In contrast, in Massachusetts, the Court found that the CAA did not reflect a congressional intent to categorically exclude GHGs and, citing several EPA memoranda, that we had not similarly foresworn all authority to regulate GHGs as a categorical matter. Id.

\46\ The D.C. Circuit majority had upheld the denial on the merits because “the EPA Administrator properly exercised his discretion under section 202(a)(1) in denying the petition for rulemaking.” Massachusetts v. EPA, 415 F.3d 50, 58 (D.C. Cir. 2005). The dissent argued that CAA section 202(a)'s breadth provided the EPA sufficient authority to regulate GHGs, that more specific authorization was not required, and that the EPA's policy justifications were inadequate reasons to deny the petitions. Id. at 67-82 (Tatel, J., dissenting).

Notably, the Court expressly declined to decide whether the EPA was required to issue an endangerment finding as to GHG emissions under the standard set out in CAA section 202(a)(1). Id. at 534 (“We need not and do not reach the question whether on remand EPA must make an endangerment finding.”). Nor did the Court address “whether policy concerns can inform EPA's actions in the event that it makes such a finding.” Id. at 534-35. Rather, the Court emphasized that the scope of its review of the denial of a rulemaking petition was “extremely limited,” id. at 527-28 (citation omitted), and held that we must respond to the petitions by deciding whether GHG emissions from new motor vehicles and engines meet the standard for regulation in CAA section 202(a)(1) or whether the science was too uncertain to make any determination, and that, in doing so, we must “ground [our] reasons for action or inaction in the statute,” id. at 535.\47\

\47\ Writing for four members of the Court, Chief Justice Roberts would have dismissed the petitions for review for lack of Article III standing. 549 U.S. at 535 (Roberts, C.J., joined by Scalia, Thomas, and Alito, J.J., dissenting). Writing for the same four members of the Court, Justice Scalia would have denied the petitions on the grounds that the Administrator reasonably exercised judgment in declining to regulate and that CAA section 302(g)'s definition of “air pollutant” does not clearly encompass CO2 and other GHGs that naturally occur in the ambient air. 549 U.S. at 549 (Scalia, J., joined by Roberts, C.J., and Thomas and Alito, J.J., dissenting).

The EPA responded to the Supreme Court's decision in Massachusetts by issuing the 2008 ANPRM. In the 2008 ANPRM, the Administrator began by noting it was “clear that if EPA were to regulate [GHG] emissions from motor vehicles under the Clean Air Act,” the interplay between CAA section 202(a)(1) and similarly worded statutory provisions “could result in an unprecedented expansion of EPA authority that would have a profound effect on virtually every sector of the economy and touch every household in the land.” 73 FR 44355. The Administrator cautioned that because the CAA was “originally enacted to control regional pollutants that cause direct health effects,” invoking authority to regulate GHG emissions “would inevitably result in a very complicated, time-consuming, and, likely, convoluted set of regulations” that “would be relatively ineffective at reducing [GHG] concentrations” and have a “potentially damaging effect on jobs and the U.S. economy.” Id.

The 2008 ANPRM echoed the Administrator's concerns by seeking public comment on invoking CAA section 202(a)(1) to regulate new motor vehicle and engine emissions in response to global climate change concerns. We acknowledged that the CAA “was not specifically designed to address GHGs,” 73 FR 44397, and that the EPA had historically interpreted and applied its CAA regulatory authorities as extending to local and regional air pollution problems, 73 FR 44408. We further noted that Congress was considering legislation to address the Nation's response to global climate change concerns and that, since Massachusetts, Congress had passed and the President had signed into law the Energy Independence and Security Act (EISA),\48\ which amended provisions applicable to the EPA's Renewable Fuels Standard (RFS) program and NHTSA's CAFE standards program. 73 FR 44398. Finally, we noted that the EPA received additional petitions to regulate stationary sources and additional GHGs, including water vapor, all of which suggested that GHG emission regulations could not readily be limited to new motor vehicles and engines. 73 FR 44399 & n.26.

\48\ Public Law 110-140, 121 Stat. 1492 (2007).

As to CAA section 202(a)(1), the 2008 ANPRM set out a framework for determining whether “GHG emissions from new motor vehicles cause or contribute to air pollution that may reasonably be anticipated to endanger public welfare” under CAA section 202(a)(1) or for “explain[ing] why scientific uncertainty is so profound that it prevents making a reasoned judgment on such a determination.” 73 FR 44398, 44421. We reviewed available information for CO2, methane, and N2O emissions and noted that HFCs, PFCs, and SF6 are “often grouped together” and separately from the rest “because they contain fluorine, typically have large global warming potentials, and are produced only through human activities.” 73 FR 44401-02.\49\ With respect to endangerment, we sought comment on whether GHGs could properly be considered air pollution that endangers public health or welfare because the potential health effects are indirect and the potential welfare effects may be positive on balance. 73 FR 44427. In addition, we sought comment on whether “the unique characteristics and properties of each GHG . . . as well as current and projected emissions” meant that each GHG should be analyzed individually or whether certain GHGs other than CO2 were amenable to grouping. 73 FR 44428. With respect to causation or contribution, we presented motor vehicle and engine emissions data for each GHG separately and noted that emission trends had diverged between pollutants, with CO2 emissions, for example, generally increasing since 1990 and N2O emissions, for example, increasing from 1990 to 1995 and then falling substantially from 1995 to 2006 because of fuel and technology changes. 73 FR 44430. We also presented extensive information on potential regulatory approaches that could be triggered by a positive finding under CAA section 202(a)(1), including approaches specific to particular GHGs. 73 FR 44438-63.

\49\ In the 2008 ANPRM, the EPA noted that the most recently available IPCC analysis concluded that “[t]he anthropogenic combined heating effect (referred to as forcing) of [methane], N2O, HFCs, PFCs and SF6 is about 40% as large as the CO2 cumulative heating effect since pre-industrial times.” 73 FR 44423.

Following a change in administration, however, the EPA proposed in April 2009 and finalized in December 2009 a much different approach to analyzing GHG emissions from new motor vehicles and engines under CAA section 202(a)(1). In the Endangerment Finding, the Administrator found that “the science [was] sufficiently certain” to compel a determination and interpreted Massachusetts as “allow[ing] for the consideration only of science.” 74 FR 66501. The Administrator interpreted Massachusetts as holding not only that “GHGs fall within the definition of `air pollutant' under the CAA,” but also as standing for the proposition “that EPA may regulate GHGs if required findings were made.” EF RTC 11:5. While expressing a “preference for comprehensive climate change legislation over the use of the current CAA to tackle climate change,” the Administrator understood the Endangerment Finding as satisfying the EPA's “duty” and “responsibility to respond to the Supreme Court's decision and to fulfill its obligations under current law.” EF RTC 11:19.\50\ In addition, the Administrator declined to consider any of the implementation challenges or options discussed in the 2008 ANPRM, asserting instead that CAA section 202(a) confers “procedural discretion” to issue standalone findings without considering a regulatory response because the statute “is silent on this issue,” 74 FR 66501, and interpreting Massachusetts as forbidding the EPA from considering in any respect the regulations that will result from an affirmative finding, 74 FR 66515.

\50\ Specifically, a variety of commenters on the proposed Endangerment Finding asserted that the Clean Air Act is ill-suited to address global climate change concerns, and that the EPA should await the results of ongoing debates and development of responsive legislation in Congress, for which both the President and the Administrator had expressed support. EF RTC 11:18-19.

The Administrator defined the relevant “air pollution” as “the combined mix of six key directly-emitted, long-lived and well-mixed [GHGs] . . . which together, constitute the root cause of human-induced climate change and the resulting impacts on public health and welfare.” 74 FR 66517. At times, the Administrator referred to the “air pollution” as the total concentration of GHGs in the atmosphere, e.g., id., and at times as only the “elevated atmospheric concentrations” of GHGs in the atmosphere as compared to pre- industrial levels, e.g., 74 FR 66523. In defining “air pollution” in this manner, the Administrator rejected arguments that the term as used in CAA section 202(a)(1) is limited to domestic concerns and airborne materials that cause direct human health effects, such as through inhalation. EF RTC 9:1-2. The Administrator reasoned that the treatment of “air pollutant” in

Massachusetts extended to the term “air pollution” directly, without the need for analysis of the difference in terminology and statutory context, and did not specifically grapple with the EPA's prior practice. Id. Notably, the Administrator excluded other “climate forcers” from this definition, including black carbon, ozone-depleting substances, nitrogen trifluoride, water vapor, and ground-level ozone. 74 FR 66520. While maintaining that these “climate forcers” could be regulated in response to global climate change concerns, the Administrator found that these substances were sufficiently different from the six “well-mixed” GHGs to warrant separate consideration. Id. As to water vapor, the Administrator reasoned that “the level of understanding is low” and that the EPA “plans to further evaluate the issues of emissions of water.” Id. And as to ground-level ozone, the Administrator reasoned that although “tropospheric ozone concentrations have exerted a significant anthropogenic warming effect since pre-industrial times,” ozone was unlike the six directly emitted, “well-mixed” GHGs because it “forms in the atmosphere from emission of pre-cursor gases.” Id.

The Administrator also defined the relevant “air pollutant” as “a single air pollutant” comprised of “the same six long-lived and directly-emitted [GHGs],” meaning the Endangerment Finding did not need to address the different characteristics or emission trends of any of the six selected GHGs individually. 74 FR 66536-37. The Administrator stated that “if in the future other substances are shown to meet the same criteria they may be added to the definition of this single air pollutant” for regulatory purposes. 74 FR 66537. Although new motor vehicles and engines “do not emit all of the substances meeting the definition of well-mixed [GHGs]”--specifically, PFCs and SF6--the Administrator found that “the reasonableness of this grouping does not turn on the particular source category being evaluated in a contribution finding.” Id.

With respect to endangerment, the Administrator began by excluding adaptation--human responses that reduce potential adverse impacts--and mitigation--independent measures that reduce the causes of potential adverse impacts--from the analysis of global climate change concerns. 74 FR 66513. The Administrator acknowledged that “some level of autonomous adaptation will occur” and that “this separation means this approach may not reflect the actual conditions in the real world in the future, because adaptation and/or mitigation may occur and change the risks.” Id. Nevertheless, the Administrator reasoned that “it would be extremely hard to make a reasoned projection of human and societal adaptation and mitigation responses” because they are “largely political” or “individual personal judgments.” Id. Next, the Administrator relied on IPCC Assessment Report 4 (AR4) projections to find that GMST would likely increase between 1.8 to 4 [deg]C by 2100, with an uncertainty range of 1.1 to 6.4 [deg]C. 74 FR 66519. Operating within this analytical framework, the Administrator found that elevated global concentrations of GHGs from all foreign and domestic sources were responsible for increased GMST that were responsible in turn for indirect health risks driven by (1) more frequent heat waves; (2) air quality effects, including increased formation of ozone, and (3) broader societal impacts related to increased frequency and severity of certain extreme weather events. 74 FR 66525.\51\ The Administrator also found that GHG emissions could lead to welfare effects related to GSLR and other downstream impacts, including (1) food production and agriculture; (2) forestry; (3) water resources; and (4) energy infrastructure and settlements, although the evidence was uncertain for several categories that may see near-term benefits. 74 FR 66531-35.\52\ Importantly, the Administrator acknowledged that the understanding of public health and welfare in the Endangerment Finding was atypical, particularly with respect to considering indirect effects and because “[n]one of th[e] human health effects are associated with direct exposure to [GHGs],” but asserted the approach was necessary given the “unique” challenge presented by global climate change. 74 FR 66527. The Administrator reasoned that many of the identified welfare impacts could be considered health impacts and that all such impacts could result indirectly from GHG “air pollution,” 74 FR 66528-29, and noted that the identified welfare impact pathways involved multiple causal steps, 74 FR 66531.\53\ In reaching these conclusions, the Administrator rejected arguments that the endangerment analysis should focus on domestic emissions and impacts on domestic ambient air and that Congress expressly provided authority when it intended the EPA to consider non- domestic air pollution. EF RTC 9:1.\54\

\51\ The Administrator also noted that increased GMST could lead to changes in certain food- and water-borne pathogens and allergens (including increases in pollen resulting from increased plant growth at higher concentrations of CO2) but did “not plac[e] primary weight on these factors.” 74 FR 66498, 66526.

\52\ The Administrator relied on welfare impacts to water resources and sea level rise as providing “the clearest and strongest support for an endangerment finding.” 74 FR 66534.

\53\ The Administrator noted that “[a]s with public health,” the analysis of “welfare” in the Endangerment Finding “considered the multiple pathways” through which “the GHG air pollution” could result in “climate change” that “affects climate-sensitive sectors,” which then leads to potential “impact . . . on public welfare.” 74 FR 66531.

\54\ For example, commenters on the proposed Endangerment Finding pointed to CAA sections 115 (authorizing the EPA to require controls when domestic emissions cause or contribute to air pollution that endangers public health or welfare in another country that has adopted reciprocal protections for emissions into the United States), 179B (authorizing the EPA to account for the impact of international emissions on State attainment of the NAAQS under certain conditions), and Title VI (providing for various authorities and obligations to address emissions that damage the ozone layer). EF RTC 9:1; see 42 U.S.C. 7415, 7509a, 7671 et seq.

With respect to contribution, the Administrator asserted broad authority to interpret the statutory standard because “[t]he language of CAA section 202(a) is silent regarding how the Administrator is to make her contribution analysis.” 74 FR 66544. Exercising that putative interpretive authority, the Administrator concluded that “it is reasonable to consider that lower percentages contribute than one may consider when looking at a local or regional problem involving fewer sources of emissions,” 74 FR 66545, because “all contributors must do their part” to avoid “a tragedy of the commons, whereby no country or source category would be accountable for contributing to the global problem of climate change,” 74 FR 66543. Next, the Administrator relied on data showing that existing motor vehicles and engines emitted four GHGs--CO2, methane, and N2O from engines, as well as HFCs from air conditioning units--that accounted for 4.3 percent of annual global GHG emissions at the time. On that basis, the Administrator found that annual GHG emissions from new motor vehicles and engines “contribute to the air pollution” consisting of the total global concentrations of the six “well-mixed” GHGs previously identified as a danger to public health or welfare. 74 FR 66537-39.

Crucially, the Endangerment Finding made clear that the EPA was acting independently from any new congressional mandate. Rather, the Administrator interpreted CAA section 202(a)(1) as setting out a standalone authority to issue findings that establish an obligation to regulate without considering implementation and purported to rest the Endangerment Finding solely on a scientific judgment

informed by the record as assembled by the Agency in 2009.

In the years since issuing the Endangerment Finding, the EPA has promulgated GHG emission standards for various classes of new motor vehicles and engines in reliance on the Endangerment Finding and, as anticipated in the 2008 ANPRM, sought to expand the same analytical framework to regulatory provisions governing existing vehicles, stationary sources, aircraft, and oil and gas operations. For a full accounting of GHG emission standards adopted since 2009 under CAA section 202(a)(1), see sections VII.B and VII.C of this preamble.

In the Endangerment Finding, the EPA treated as out of scope the impacts of extending CAA section 202(a)(1) to address global climate change concerns on other CAA provisions with similar endangerment provisions. See, e.g., EF RTC 11:20-23. However, the EPA soon finalized the first set of GHG emission standards for new motor vehicles and engines \55\ alongside related rules establishing GHG emission thresholds for stationary source permitting under the Prevention of Significant Deterioration (PSD) program and Title V.\56\ Several years later, the EPA again relied on the Endangerment Finding to extend the GHG regulatory program to new and existing stationary source performance standards and guidelines for power plants under CAA section 111.\57\

\55\ 75 FR 25324 (May 7, 2010).

\56\ “Reconsideration of Interpretation of Regulations That Determine Pollutants Covered by Clean Air Act Permitting Programs,” 75 FR 17004 (Apr. 2, 2010) (“Triggering Rule”); “Prevention of Significant Deterioration and Title V Greenhouse Gas Tailoring Rule,” 75 FR 31514 (June 3, 2010) (“Tailoring Rule”).

\57\ “Standards of Performance for Greenhouse Gas Emissions From New, Modified, and Reconstructed Stationary Sources: Electric Utility Generating Units,” 80 FR 64510 (Oct. 23, 2015) (“2015 NSPS”); “Carbon Pollution Emission Guidelines for Existing Stationary Sources: Electric Utility Generating Units,” 80 FR 64662 (Oct. 23, 2015) (“Clean Power Plan”). The EPA also cited the Endangerment Finding to reach a similar conclusion for aircraft under CAA section 231. “Finding That Greenhouse Gas Emissions From Aircraft Cause or Contribute to Air Pollution That May Reasonably Be Anticipated To Endanger Public Health and Welfare,” 81 FR 54422 (Aug. 15, 2016).

In Coalition for Responsible Regulation, the D.C. Circuit rejected petitions for review of the Tailpipe Rule, Triggering Rule, Tailoring Rule, and the underlying Endangerment Finding. As relevant here, the court read Massachusetts as precluding us from declining to regulate for policy reasons that “were not part of the calculus” and, citing generally to the entirety of the Massachusetts decision, as holding that the “EPA indeed wields the authority to regulate greenhouse gases under the CAA.” 684 F.3d at 118. Applying this reading, the court rejected petitioners' arguments that we should have considered the “` absurd' ” results for stationary source permitting when issuing the Endangerment Finding. Id. The court understood the interpretation of the statutory definition of “air pollutant” in Massachusetts to apply anywhere that term is used in the substantive provisions of the CAA. Id. at 134-44. The court acknowledged that “nothing in the CAA requires regulation of a substance simply because it qualifies as an `air pollutant' under this broad definition.” Id. at 135. Applying its understanding of Massachusetts, however, the court held that reading “air pollutant” as “any regulated air pollutant” was “compelled by the statute” and rejected petitioners' arguments that the PSD provisions should be read in context as focusing on localized “air pollution” problems. Id. at 134, 138.\58\

\58\ The D.C. Circuit subsequently denied rehearing en banc. See Coal. for Responsible Regulation v. EPA, 2012 U.S. App. LEXIS 25997 (Dec. 20, 2012). Judge Brown dissented, arguing that the CAA was designed to address “the harmful effects of poisoned air on human beings and their local environs,” that such important policy decisions were for Congress to decide, and that the panel had overread “dicta” in Massachusetts. Id. at * 29-62. Then-Judge Kavanaugh also dissented, arguing that we exceeded our statutory authority in regulating GHG emissions under the PSD program by failing to read the term “air pollutant” in context and that the issue was “plainly one of exceptional importance” that Congress should decide. Id. at * 62-93.

In UARG, the Supreme Court held that the EPA exceeded its authority under the CAA in its approach to extending stationary source permitting to cover GHG emissions. The Court rejected the D.C. Circuit's application of Massachusetts in this context as a “flawed syllogism,” 573 U.S. at 316, holding that “while Massachusetts rejected EPA's categorical contention that greenhouse gases could not be `air pollutants' for any purposes of the Act, it did not embrace EPA's current, equally categorical position that greenhouse gases must be air pollutants for all purposes regardless of the statutory context,” id. at 319 (cleaned up). Rather, “Massachusetts does not foreclose the Agency's use of statutory context to infer that certain of the Act's provisions use `air pollutant' to denote not every conceivable airborne substance, but only those that may sensibly be encompassed within the particular regulatory program.” Id. The Court went on to reject our interpretation that required a permit based on GHG emissions as “` incompatible' with `the substance of Congress' regulatory scheme' ” and inconsistent with the principle that “Congress . . . speak[s] clearly if it wishes to assign to an agency decisions of vast `economic and political significance.' ” Id. at 322-24 (quoting Brown & Williamson, 529 U.S. at 156, 159).\59\

\59\ Writing for four Justices in a partial dissent, Justice Breyer argued that the statute could be interpreted to encompass certain stationary sources based on their volume of GHG emissions. 573 U.S. at 334-43 (Breyer, J., joined by Ginsburg, Sotomayor, and Kagan, J.J.). Writing for two Justices in a partial dissent from a different holding, Justice Alito argued that the case demonstrated that Massachusetts was wrongly decided and that the majority erred in holding that permitted sources that emit conventional pollutants could be required to install control technologies for GHGs. Id. at 343-50 (Alito, J., joined by Thomas, J.).

Soon thereafter, both courts weighed in on the extension of the GHG regulatory program to power plants under CAA section 111. The Supreme Court stayed the 2015 Clean Power Plan pending review by the D.C. Circuit, which had denied a stay.\60\ The D.C. Circuit subsequently reviewed a later rulemaking that repealed the Clean Power Plan and replaced it in part.\61\ In American Lung Association v. EPA, 985 F.3d 914 (D.C. Cir. 2021), a divided panel reinstated the 2015 Clean Power Plan and vacated the 2019 ACE Rule. Among other things, the panel majority held that the major questions doctrine has no application to the scope of our CAA section 111 authority, id. at 959-61, and rejected the argument that generation shifting was an impermissible use of our regulatory authority, id. at 966-68. The panel majority also rejected challenges to the endangerment and significant contribution bases for regulating GHGs under CAA section 111, citing Coalition for Responsible Regulation and stating that if “greenhouse gas emissions by fossil- fuel-fired power plants” do not “significantly contribute” to global climate change, it would be “nigh impossible for any source of greenhouse gas pollution to cross that statutory threshold.” Id. at 977.\62\

\60\ West Virginia v. EPA, 136 S Ct. 1000 (2016).

\61\ “Affordable Clean Energy Rule,” 84 FR 32520 (July 8, 2019) (“2019 ACE Rule”).

\62\ In a partial dissent, Judge Walker argued that the 2015 Clean Power Plan (and aspects retained in the 2019 ACE Rule) violated the major questions doctrine because CAA section 111 does not include a clear statement of authority to regulate GHG emissions from power plants. Am. Lung Ass'n, 985 F.3d at 995-1003 (pointing to failed legislation in 2009 that would have provided the requisite authority to regulate GHG emissions from power plants).

In West Virginia, the Supreme Court reversed the D.C. Circuit's treatment of the major questions doctrine and held that the 2015 Clean Power Plan exceeded our authority to regulate existing sources under CAA section 111(d). The Court surveyed UARG, Brown & Williamson, and additional precedents to confirm that an agency must have more than “a colorable textual basis” to assert “ `unheralded' regulatory power over `a significant portion of the American economy.' ” 597 U.S. at 721-23 (quoting UARG, 573 U.S. at 324). In such cases, “both separation of power principles and a practical understanding of legislative intent” require the agency to “point to `clear congressional authorization' for the power it claims.” Id. at 723 (quoting UARG, 573 U.S. at 324). The Court held that our reliance on CAA section 111(d) to regulate GHG emissions was “a major questions case” because we had asserted the power “to substantially restructure the American energy market.” Id. at 724. That provision “had rarely been used in the preceding decades,” and we had used it in an “unprecedented” manner “to adopt a regulatory program that Congress had conspicuously and repeatedly declined to enact itself.” Id. at 724-28. Since we lacked express authorization, the Court concluded that we lacked statutory authority for the 2015 Clean Power Plan. Id. at 732-35.\63\

\63\ In dissent, Justice Kagan argued that the Court had obstructed the EPA's efforts to regulate GHG emissions: “Today, the Court strips the [EPA] of the power Congress gave it to respond to `the most pressing environmental challenge of our time.” West Virginia, 597 U.S. at 753 (Kagan, J., joined by Breyer and Sotomayor, J.J., dissenting) (quoting Massachusetts, 549 U.S. at 505); see also id. at 755 (“This Court has obstructed EPA's effort from the beginning.”).

Following the Endangerment Finding, the EPA also received multiple petitions for reconsideration from industry groups, States, and various organizations arguing that our approach in 2009 was legally and scientifically flawed and that external assessments by the IPCC, among others, had not adequately addressed recent criticisms of climate change science. The EPA denied these consolidated petitions in 2010 without notice and comment (“2010 Denials”). Reiterating the scientific assertions from the technical support document (TSD) used in 2009, we emphasized that we had conducted an independent review of outside assessments in issuing the Endangerment Finding and asserted that the core conclusions of the Endangerment Finding remained valid notwithstanding the flaws raised by the petitioners. The EPA also issued a volume of response documents defending the methodologies and experts relied upon and concluded that no new information warranted reconsideration. 75 FR 49556.\64\

\64\ The D.C. Circuit rejected several petitions for review of the 2010 Denials as part of the Coalition for Responsible Regulation decision. 684 F.3d at 124-26.

In April 2022, the EPA denied, again without notice and comment, a new round of petitions for reconsideration and rulemaking asserting that the Endangerment Finding was legally and scientifically flawed and undermined by more recent scientific assessments (“2022 Denials”). We acknowledged that several recent studies contradicted assessments by the USGCRP and IPCC but reaffirmed our earlier position that such assessment reports are entitled to greater weight than dissenting views.\65\ We also considered criticisms of the EPA's SCC methodology out of scope because “the social cost of carbon played no role in the 2009 Endangerment Finding.” \66\ We further acknowledged that severing the endangerment and cause or contribute analysis from the development of subsequent regulations had impacted the EPA's approach to GHG emission standards, including because the SAB did not have the opportunity to review the Endangerment Finding as would otherwise have been required by the CAA.\67\ Nevertheless, we reaffirmed our position that CAA section 202(a) grants “procedural discretion” to issue findings and emission standards separately and “decline[d] to exercise that discretion” differently.\68\

\65\ 2022 Denials at 15-17.

\66\ Id. at 30.

\67\ Id. at 36 (noting that 42 U.S.C. 4365(c)(1) requires SAB consultation for a “standard” promulgated under CAA section 202(a) but asserting that requirement does not extend to “findings” issued under the same provision).

\68\ Id. at 39.

Since the EPA published the 2009 Endangerment Finding, there have been developments in innovation, science, economics, and mitigation, as well as significant Supreme Court decisions that provide new guidance on how Federal agencies should interpret the statutory provisions that Congress has tasked them with administering.\69\ Accordingly, the Administrator determined that the Endangerment Finding should be reconsidered to address legal and scientific developments that present reason to question the ongoing validity and reliability of its conclusions and to subject these important issues to public comment for the first time since 2009.

\69\ See Feb. 19, 2025 Memo at 1.

In initiating reconsideration, the Administrator explored all findings, support, questions, and ambiguities contained within the science relied upon by the Endangerment Finding. On July 29, 2025, the Administrator signed a proposed rule setting out the results of the EPA's reconsideration to date and proposing to rescind the Endangerment Finding and all GHG emission standards for LD, MD, and HD motor vehicles and engines promulgated since 2009 under CAA section 202(a)(1). At proposal, we noted that the Endangerment Finding itself and subsequent reports, studies, and analyses had acknowledged significant questions and ambiguities presented by the observable realities of the past nearly two decades and the recent findings of the scientific community. We also noted that there may be as-yet- unidentified issues or discrepancies present in the underlying technical analysis and scientific justifications offered in the Endangerment Finding. Finally, we noted that when confronted with science offering a diverse array of conclusions, methodologies, and explanations, the Administrator strove to inform his judgment to the most impartial extent possible.

In reviewing the public response to the proposal, the Administrator appreciated the wide variety of perspectives and significant interest in the issues raised for further consideration. In particular, the Administrator carefully examined the additional data, modeling, and information submitted in connection with our request for comment on the impact of the EPA's GHG emission standards for new motor vehicles and engines to date and the efficacy of such regulations in addressing the risks identified in the Endangerment Finding. The EPA has conducted further analysis to evaluate the competing perspectives on the ability of GHG emission standards to have a material (i.e., non-de minimis) impact on global climate change concerns, with a particular focus on trends in GMST and GSLR--key metrics commonly derived from climate models and primary drivers of the Agency's causal analysis of endangerment in the 2009 Endangerment Finding.

As discussed in section IV of this preamble, the EPA concludes that it lacks statutory authority to resolve these questions through regulatory findings and emission standards under CAA section 202(a)(1). That conclusion led the Administrator to rest this final action on the legal bases proposed as the

primary rationale for rescission of the Endangerment Finding and repeal of associated GHG emission standards, as explained in sections V.A and V.B of this preamble. As a separate but complementary basis for rescission and repeal, the Administrator finds that the available evidence indicates GHG emission standards under CAA section 202(a)(1) do not impact trends in GMST or GSLR in any material way, let alone the health and welfare impacts attributed to such trends in the Endangerment Finding. As discussed in section V.C of this preamble, this conclusion further indicates that the best reading of CAA section 202(a)(1) does not encompass the regulation of “air pollution” in the form of global climate change concerns and serves as an independent basis for repealing the GHG emission standards. For discussion of public comments received on the alternative climate science basis and the Administrator's decision not to finalize on that ground in favor of future opportunities for fact finding and public engagement, see section VI of this preamble.

The statutory authority for this final action is the same as that relied upon in the prior actions at issue: CAA section 202(a)(1), which requires the Administrator to “prescribe” and “from time to time revise . . . standards” for certain air pollutants emitted by new motor vehicles and new motor vehicle engines “in accordance with the provisions of this section.” \70\ In addition, unless provided otherwise by statute, an agency may revise or rescind prior actions so long as it acknowledges the change in position, provides a reasonable explanation for the new position, and considers legitimate reliance interests in the prior position.\71\

\70\ 42 U.S.C. 7521(a)(1).

\71\ See FDA v. Wages & White Lion Invs., L.L.C., 604 U.S. 542, 568-70 (2025); FCC v. Fox Television Stations, Inc., 556 U.S. 502 (2009); Motor Vehicle Mfrs. Ass'n v. State Farm Mut. Auto. Ins. Co., 463 U.S. 29 (1983).

Nothing in the language of the relevant statutory provision prohibits or conditions our general authority to rescind prior actions through rulemaking. CAA section 202(a)(1) grants the Administrator discretion to “revise” standards prescribed “in accordance with the provisions of this section” and does not require retaining the same level of stringency when revising or rescinding existing standards. Moreover, the statute neither authorizes the Administrator to issue standalone findings that trigger a duty to regulate nor prohibits the Administrator from rescinding such findings. Rather, CAA section 202(a)(1) requires the Administrator to prescribe standards for emissions of any air pollutant by classes of new motor vehicles or engines when, in his judgment, emissions of such air pollutant by such classes of new motor vehicles or engines “cause, or contribute to, air pollution which may reasonably be anticipated to endanger public health or welfare.” Notably, the EPA has consistently assumed that it has the statutory authority to rescind the Endangerment Finding in reviewing the merits of petitions for reconsideration since 2009 and did not state that we lack such reconsideration authority.\72\

\72\ See, e.g., 2022 Denials at 7-10 (denying mandatory reconsideration under CAA section 307(d) and reviewing the petitions on the merits as rulemaking petitions under APA section 553(e)); 75 FR 49556, 49560-63 (Aug. 13, 2010) (denying mandatory reconsideration under CAA section 307(d) without asserting that the EPA lacked statutory authority to rescind or revise the Endangerment Finding).

The EPA acknowledges that rescinding the Endangerment Finding involves significant changes to the legal interpretations adopted in the Endangerment Finding and retained in subsequent actions. For example, the interpretation of CAA section 202(a) that we are finalizing precludes the EPA from issuing standalone endangerment and contribution findings and instead requires the Agency to make findings for particular air pollutant emissions and classes of new motor vehicles and engines as an integral step in a rulemaking to prescribe standards for such emissions and classes, consistent with our decades- long practice prior to 2009 in regulating non-GHG air pollutants. Furthermore, the interpretation of CAA section 202(a)(1) that we are finalizing in this action reverses the basis for the Endangerment Finding by concluding that global climate change concerns cannot satisfy the statutory standard for regulation under CAA section 202(a)(1). This interpretation is the best reading of the statute, and it is different from the final actions taken by the Agency since 2009 with respect to GHG emission standards under CAA section 202(a).\73\ For example, we acknowledge that the EPA changed its position in 2009 and argued in actions finalized since that time and in briefs filed in defense of those actions that CAA section 202(a) authorizes us to regulate in response to global climate change concerns.\74\ We also acknowledge that the EPA argued in actions finalized since 2009 and in briefs filed in defense of those actions that the major questions doctrine has no application to CAA section 202(a)(1).\75\ However, intervening legal developments must be considered when evaluating these statements as they developed over time. We initially developed those novel positions without the benefit of the Supreme Court's decisions in UARG, Michigan, and West Virginia, which explained and applied the major questions doctrine to related GHG emission regulations. Moreover, we note that each of these major actions and rules predated the Supreme Court's decision in Loper Bright, which overruled Chevron deference to agency statutory interpretation and clarified that statutes have a single, best meaning.\76\ In light of these decisions and upon further review of the EPA's prior statements on the applicability and impact of the major questions doctrine, we are finalizing, as proposed, a new position that more faithfully adheres to precedent and governing legal principles. For discussion of CAA section 202(a)(1) and related statutory provisions interpreted in this final action, see section V of this preamble.

\73\ See, e.g., 74 FR 66496 (Dec. 15, 2009); 75 FR 25324 (May 7, 2010); 76 FR 57106 (Sept. 15, 2011); 77 FR 62624 (Oct. 15, 2012); 81 FR 73478 (Oct. 25, 2016); 85 FR 24174 (Apr. 30, 2020); 86 FR 74434 (Dec. 30, 2021); 89 FR 27842 (Apr. 18, 2024); 89 FR 29440 (Apr. 22, 2024).

\74\ See, e.g., 74 FR 66496, 66524 (Dec. 15, 2009) (Endangerment Finding); 2022 Denials at 1; 75 FR 49556 (Aug. 13, 2010) (2010 Denials).

\75\ See, e.g., 89 FR 29440, 29468-70 (Apr. 22, 2024) (2024 HD GHG Emission Standards Rule) (arguing that regulation of GHG emissions under CAA section 202(a) in response to global climate change concerns is not a question of significant importance, that the EPA has clear congressional authorization, and that use of this authority since 2009 is not novel); 89 FR 27842, 27897 (Apr. 18, 2024) (2024 LD and MD Multi-Pollutant Emission Standards Rule) (same). In these final rules, the EPA also took the position-- repudiated in this final action--that it is permissible to expect manufacturers to comply with GHG emission standards by shifting to EVs.

\76\ 603 U.S. at 412-13 (overruling Chevron U.S.A., Inc. v. NRDC, Inc., 467 U.S. 837 (1984)).

The EPA is also finalizing that GHG emission standards for new motor vehicles and engines are futile because they have no material (i.e., non-de minimis) impact on the global climate change concerns animating this regulatory program and is reaching two separate and independent conclusions as a result. First, we conclude that futility lends further support to the understanding that CAA section 202(a)(1) is best read to encompass “air pollution” that endangers human health and the environment through local and regional exposure and that domestic regulation can impact without requiring

international emissions reductions. Second, we conclude that futility warrants repeal of the GHG emission standards independent from the Endangerment Finding because they impose immense burdens without furthering any statutory objective. These additional bases for this final action represent a change from the novel position taken in actions and rulemakings since 2009 to prescribe and revise GHG emission standards under CAA section 202(a)(1).\77\ For example, we asserted in the Endangerment Finding that the ability of GHG emission standards to impact global climate change concerns was outside the scope of the CAA section 202(a)(1) endangerment and contribution analysis, 74 FR 66501- 02, that we could not consider the degree of emissions reductions that could be achieved by regulations issued as a result of the findings, 74 FR 66507-08, and that the “unique” nature of global climate change concerns justified accepting a different analysis than that traditionally applied to mobile-source air pollution problems, 74 FR 66538, 66543. In GHG emission standard rulemakings since 2009, we analyzed the impact of potential standards in terms of contribution, i.e., tons of emissions, rather than impact on endangerment, i.e., from trends in GMST and GSLR that lead in turn to the health and welfare impacts predicted in the Endangerment Finding. That is, we generally evaluated potential GHG emissions reductions (in tons of CO2 equivalent) \78\ and used SCC methodologies to attach a dollar value to such emissions reductions.\79\ See section V.C of this preamble for further discussion of these additional rationales and the EPA's prior positions.

\77\ See, e.g., 74 FR 66496, 66524 (Dec. 15, 2009); 75 FR 25324 (May 7, 2010); 76 FR 57106 (Sept. 15, 2011); 77 FR 62624 (Oct. 15, 2012); 81 FR 73478 (Oct. 25, 2016); 85 FR 24174 (Apr. 30, 2020); 86 FR 74434 (Dec. 30, 2021); 89 FR 27842 (Apr. 18, 2024); 89 FR 29440 (Apr. 22, 2024).

\78\ See, e.g., 75 FR 25324 (May 7, 2010).

\79\ See, e.g., 89 FR 29440, 29675 (Apr. 22, 2024) (2024 HD GHG Emission Standards Rule) (“While the EPA did not conduct modeling to specifically quantify changes in climate impacts resulting from this rule in terms of avoided temperature change or sea-level rise, the Agency did quantify climate benefits by monetizing the emission reductions through the application of estimates of the social cost of greenhouse gases (SC-GHGs).”); 89 FR 27842, 28099 (Apr. 18, 2024) (2024 LD and MD Multi-Pollutant Emission Standards Rule) (same).

The EPA further acknowledges that repealing the GHG emission standards based on the proposed rescission of the Endangerment Finding is a departure from our position in rulemakings since 2009 that prescribed and revised GHG emission standards for LD, MD, and HD vehicles and engines under CAA section 202(a)(1). This rescission eliminates the statutory basis for those standards because we relied on the Endangerment Finding in each rulemaking to invoke our authority under CAA section 202(a)(1) without making the required findings for GHGs emitted by the class or classes of new motor vehicles or engines at issue in each rulemaking. To the extent we reaffirmed the Endangerment Finding in subsequent standard rulemakings, the conclusions we are finalizing in this action eliminate the improperly claimed statutory basis for such reaffirmations, all of which relied on the same underlying interpretation of CAA section 202(a)(1) as encompassing the regulation of GHG emissions based on global climate change concerns. See section VII of this preamble for further discussion of each prior rulemaking and the regulatory changes we are making to repeal all GHG emission standards currently in effect for new motor vehicles and engines on bases finalized in this action.

As discussed throughout this preamble, the EPA is finalizing these changes to comply with limits on our statutory authority under the best reading of CAA section 202(a)(1), adhere to the legal limits on our power to set national policy within our constitutional system of democratic government, and realign Agency resources to prioritize core statutory responsibilities that protect human health and the environment. Importantly, the Nation's policy response to global climate change concerns was a major issue in the 2024 presidential election, in which voters were presented with distinct legal and policy approaches and elected a candidate promising a change in policy. Under these circumstances, the election of a new Administration is an independent and sufficient basis for reassessing and revising legal interpretations to faithfully adhere to the best reading of the statute.\80\ Democratic accountability is essential to the exercise of delegated authority by administrative agencies,\81\ and retaining the Endangerment Finding and associated GHG emission standards without clear statutory authority would frustrate, not promote, constitutional values and the rule of law. The EPA lacks authority to retain the Endangerment Finding under the best reading of CAA section 202(a)(1), and the statute controls regardless of policy preferences.\82\

\80\ See State Farm, 463 U.S. at 59 (Rehnquist, J., concurring in part and dissenting in part); PETA v. USDA, 918 F.3d 151, 158 (D.C. Cir. 2019) (“new administrations are entitled to reevaluate and modify agency practices, even longstanding ones”); Nat'l Ass'n of Home Builders v. EPA, 682 F.3d 1032, 1043 (D.C. Cir. 2012) (“the inauguration of a new President and the confirmation of a new EPA Administrator” went “a long way toward explaining why EPA” changed policy).

\81\ See, e.g., U.S. Telecom Ass'n v. FCC, 855 F.3d 381 (D.C. Cir. 2017) (Brown, J., dissenting from denial of rehearing en banc); Elena Kagan, Presidential Administration, 114 Harv. L. Rev. 2245, 2252-53, 2332-34 (2001).

\82\ Loper Bright, 603 U.S. at 403; West Virginia, 597 U.S. at 735; UARG, 573 U.S. at 325.