On July 29, 2025, the U.S. Environmental Protection Agency (“EPA”) issued a series of alternative proposals seeking to repeal greenhouse gas (“GHG”) emissions standards for new vehicles such as cars, trucks and motorcycles, including standards that have required vehicle manufacturers to control vehicle GHG emissions for over a decade. The proposals also would repeal EPA's 2009 determination that GHGs emitted by new vehicles in the United States contribute to air pollution that may endanger public health or welfare.1
EPA Argues That it Exceeded its Authority in 2009
One of EPA's alternatives proposes that EPA's 2009 determination exceeded EPA's authority by considering global GHG emissions and climate change, instead of evaluating only local exposure. EPA asserts in its July proposal that it does not have the authority to regulate GHG emissions from new vehicles because EPA's authority under the federal Clean Air Act applies only to air pollution that endangers public health or welfare itself through local exposure. The proposal concludes that the GHGs identified in EPA's 2009 determination -- carbon dioxide, methane, nitrous oxide, hydrofluorocarbons, perfluorocarbons and sulfur hexafluoride -- do not themselves endanger public health or welfare through local exposure. As an example, the proposal explains that carbon dioxide is not, by itself, harmful to human health in localized concentrations the way that other gases – such as carbon monoxide – can be. Because the 2009 finding pointed to climate change as the endangering factor to public health or welfare, and not to local exposure to the gases themselves, EPA's recent proposal explains that EPA's 2009 determination was improper under the federal Clean Air Act.
The proposal also argues that EPA's 2009 determination improperly separated the question of whether new vehicle engines contribute to GHG concentrations from the question of whether GHGs endanger public health or welfare. Instead, the agency now maintains that in order to regulate new vehicle GHG emissions as it has since 2009, the federal Clean Air Act requires EPA to find that the specific vehicle pollutant emissions and classes of vehicles cause or contribute to air pollution endangering public health or welfare without relying on emissions from other sources regulated under other Clean Air Act provisions.
EPA Questions its 2009 Scientific Conclusions
Another alternative that EPA sets out in the proposal explains that, even if EPA had the authority to make the finding it made in 2009, scientific developments since 2009 have called into question the premises, assumptions and conclusions of that 2009 endangerment finding. The proposal casts doubt on whether EPA would conclude today that new vehicle GHG emissions contribute to air pollution that may endanger public health or welfare in light of ongoing uncertainties in the relevant scientific data. EPA explains that it has serious concerns that many of the scientific underpinnings of its 2009 finding are materially weaker than previously believed, and are contradicted by empirical data, peer-reviewed studies and scientific developments since 2009. The proposal further notes that global atmospheric GHG concentrations have continued to rise since EPA issued its 2009 finding and began regulating GHG emissions under the federal Clean Air Act. Nevertheless, EPA explains that this increase in atmospheric GHG concentrations has not produced the degree of adverse impacts to public health and welfare that EPA anticipated in its 2009 finding. In the proposal, EPA says that extreme weather events – such as hurricanes and flooding – have not demonstrably increased relative to historic highs, and that aggregate sea level rise has been minimal.
EPA Says No Technology Would Measurably Affect GHG Concentrations From New US Vehicle Emissions
The proposal explains that the GHG emissions standards for vehicles should be repealed because there is no existing technology that would measurably affect GHG concentrations in the atmosphere from new U.S. vehicle emissions. EPA goes on to describe how reducing GHG emissions from new vehicles in the United States to zero would not have a scientifically measurable impact on global GHG concentrations and climate trends.
EPA Says GHG Emissions Standards May Be Harmful
Finally, the proposal also states that GHG emissions standards actually harm public health and welfare by increasing prices, decreasing consumer choice, and slowing replacement of old vehicles that are less safe and emit a greater volume and variety of pollutants than new vehicles. EPA explains that it has serious concerns that its GHG standards may be harming air quality by raising prices and reducing fleet turnover.
EPA Relies on Changes in Law Since 2009
The proposal relies on the recent Loper Bright and West Virginia Supreme Court decisions to support EPA's proposed change from the approach EPA took in 2009.2 EPA explains that these decisions, which had not been handed down when EPA made its determination in 2009, support EPA's current proposed approach because the decisions clarify that EPA cannot use the Clean Air Act to take an action that would have such an economically and politically significant impact as regulating vehicle GHG emissions or global climate change without express congressional authorization to do so.
Next Steps
EPA's July proposals will be available for public comment until September 21, 2025. Legal challenges to the proposals are likely, including on the basis that the Supreme Court has previously affirmed EPA's authority to regulate GHG emissions from new vehicles under the Clean Air Act, and that climate science has arguably significantly advanced since the endangerment finding was first issued in 2009.3 Courts have consistently upheld the endangerment finding, with the Supreme Court doing so as recently as December 2023, when it turned down a request to revisit a ruling by the U.S. Court of Appeals for the District of Columbia Circuit that rejected a challenge to the finding.4
n addition to preventing EPA from issuing or enforcing GHG emissions standards for new vehicles, EPA's proposals may impact climate change litigation in U.S. courts and other U.S. federal GHG emissions laws beyond those for vehicles. This is because EPA's 2009 finding, which EPA is now proposing to repeal, has served as a legal basis for other U.S. federal GHG emissions regulations impacting sectors outside of vehicles, along with preemption defenses asserted by energy company defendants in climate change litigation brought by local governments. EPA addresses this issue in its proposal, explaining that the federal Clean Air Act would continue to preempt any state or local standard relating to emissions control because new vehicles that had been subject to GHG emission standards would remain subject to Clean Air Act vehicle emission standards for non-GHG pollutants. EPA further explains that the Clean Air Act would continue to preempt federal common law claims for GHG emissions because Congress delegated to EPA the decision of whether and how to regulate such emissions.
The proposal does leave open the possibility for future U.S. federal regulation of vehicle GHG emissions. EPA explains that the bases of its proposed repeal would not foreclose EPA from regulating carbon dioxide, methane, nitrous oxide, hydrofluorocarbons, perfluorocarbons and sulfur hexafluoride emissions from new vehicles if EPA determines that one or more of those GHGs meet the requirements for regulation under the Clean Air Act as interpreted by EPA in the July proposal.
Footnotes
1. See “Reconsideration of 2009 Endangerment Finding and Greenhouse Gas Vehicle Standards,” Environmental Protection Agency (July 29, 2025).
2. Loper Bright Enterprises v. Raimondo, 603 U.S. 369 (2024); West Virginia v. EPA, 597 U.S. 697 (2022).
3. Massachusetts v. EPA, 549 U.S. 497 (2007).
4. Concerned Household Electricity Consumers Council, et al. v. EPA, Case No. 22-1139 (D.C. Cir. 2023), cert. denied.
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