Today, August 1, 2025, the US Environmental Protection Agency (EPA) published a controversial proposed rule that, if finalized, would rescind the agency’s landmark 2009 determination that greenhouse gas (GHG) emissions from motor vehicles and engines contribute to air pollution that endangers public health and welfare (the Endangerment Finding).
That regulatory finding is the essential predicate for federal regulation of motor vehicle and engine GHG emissions. Based on rescission of the Endangerment Finding, the proposal would repeal all GHG emission standards for new light-, medium-, and heavy-duty vehicles and engines sold in the US.
Resetting US climate and transportation policy
Announcing the proposed rule, EPA Administrator Lee Zeldin criticized existing GHG emissions regulations as ineffective in addressing climate change, and focused on the cost of compliance with EPA’s GHG tailpipe standards, describing them as “hidden taxes on American businesses and families” costing them “$1 trillion or more.”
EPA’s proposal responds to a directive of President Donald Trump’s Executive Order “Unleashing American Energy” (issued the day he took office), ordering the agency to submit recommendations to the White House regarding the “legality and continuing applicability” of the Endangerment Finding.
In March 2025, EPA recommended reconsideration of the Endangerment Finding and all regulations and actions grounded in that Finding. The new proposed rule formally initiates the process of rescinding the foundational Endangerment Finding.
EPA’s action is part of a broader effort by the Trump Administration and congressional Republicans to change US climate policy by eliminating programs or regulations they consider too costly or ineffective, particularly policies affecting the transportation and energy sectors.
In May 2025, Congress passed – and President Trump signed – Congressional Review Act (CRA) resolutions revoking waivers issued by EPA that authorized California’s separate GHG standards for light- and heavy-duty vehicles and nonroad engines. However, use of the CRA to revoke the waivers is subject to a pending court challenge.
In addition, the One Big Beautiful Bill Act, signed into law on July 4, 2025, eliminated monetary penalties for noncompliance with federal corporate average fuel economy (CAFE) standards set by the National Highway Traffic Safety Administration, and terminated tax credits for electric vehicles. The common rationale for these and related Trump Administration actions is that eliminating GHG vehicle emission standards will reduce energy and transportation costs while increasing choice for consumers and businesses.
Background on the Endangerment Finding
The Clean Air Act (CAA) requires EPA to regulate tailpipe emissions from new motor vehicles and engines. Specifically, Section 202(a)(1) of the CAA requires EPA to prescribe by regulation “standards applicable to the emission of any air pollutant from any class or classes of new motor vehicles or new motor vehicle engines, which in [EPA’s] judgment cause, or contribute to, air pollution which may reasonably be anticipated to endanger public health or welfare.”
In 2007, the US Supreme Court issued Massachusetts v. EPA, a 5–4 decision concluding that the CAA’s broad definition of “air pollutant” includes GHGs. Therefore, the Court ruled, Section 202(a)(1) of the CAA grants EPA the statutory authority to regulate GHG emissions from new motor vehicles and engines. The high court decision left to EPA’s judgment the determination of whether GHG emissions from vehicles cause or contribute to conditions (eg, climate change) that endanger public health or welfare.
Chief Justice John Roberts, joined by two other justices who still serve on the Court (Justices Clarence Thomas and Samuel Alito) dissented in Massachusetts v. EPA. While that dissent focused on the Commonwealth of Massachusetts’ standing to bring the lawsuit, it also suggested that the majority (none of whom serve on the Court today) “ignores the complexities of global warming” and opined that there is an “evident mismatch” between “catastrophic global warming – and the narrow subject matter of the Clean Air Act provision [for motor vehicles].”
Following the Supreme Court’s decision, EPA issued the Endangerment Finding, concluding that six GHGs – carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF6) – emitted from motor vehicles and engines contribute to air pollution at concentrations projected to threaten public health and welfare.
Based on that finding, EPA promulgated vehicle GHG emissions standards, which took effect in model years 2012 (light-duty vehicles) and 2014 (medium- and heavy-duty vehicles). Those standards have generally increased in stringency for each successive model year. Current EPA GHG tailpipe emissions standards extend through model year 2032.
EPA has also relied on the Endangerment Finding, in part, to support other GHG emissions regulations under other CAA provisions, including standards for stationary sources (eg, power plants) and aircraft engines. The Endangerment Finding thus forms a significant part of the foundation for various GHG and climate change mitigation regulations and policies that EPA has implemented over the past decade.
Proposal to rescind the Endangerment Finding
EPA’s new proposal proffers legal and factual rationales for rescinding the Endangerment Finding and repealing federal GHG emission standards for vehicles and engines.
Legal bases for proposed rescission of the Endangerment Finding
Some of the key components of EPA’s revised legal analysis and interpretation of its authority under the CAA include:
- Air pollution subject to regulation: EPA proposes to interpret the term “air pollution” as exclusively referring to local or regional exposure to air pollutants, not global risks associated with global emissions of air pollutants such as GHGs.
- Procedural requirements for the Endangerment Finding: EPA also proposes to find that the CAA does not grant it power or discretion to issue a general endangerment finding in isolation, based on GHGs with elevated concentrations in the upper atmosphere (not all of the GHGs covered by the Endangerment Finding are contained in vehicle tailpipe emissions). Instead, EPA asserts, the statute only authorizes such a finding based on a narrower set of GHGs that EPA determines are associated with vehicle tailpipe emissions. Thus, EPA concludes, the agency previously acted outside its authority when issuing the broader Endangerment Finding.
- Regulated emissions must cause or contribute to endangerment: EPA’s proposal would further find that the CAA requires EPA to establish a causal connection between new motor vehicle GHG emissions and endangerment to public health or welfare caused by climate change. Thus, the proposed rule would conclude, the Endangerment Finding erroneously relied on global GHG emissions and stationary sources of GHG emissions regulated by other sections of the CAA to justify its finding regarding motor vehicle emissions.
EPA finds further legal support for its proposed withdrawal of the Endangerment Finding in the Supreme Court’s recent decisions in Loper Bright Enterprises v. Raimondo (eliminating Chevron deference to agency interpretations of ambiguous statutes) and West Virginia v. EPA (the “major question” doctrine).
Citing Loper Bright and the absence of specific statutory authorization to regulate GHG emissions, the proposed rule contends that EPA may not rely on statutory silence or ambiguity to justify the agency’s interpretation of CAA Section 202(a).
Relying on the major question doctrine adopted in West Virginia, EPA would further find that regulating motor vehicle GHG emissions is an economically and politically significant issue requiring a clear directive from Congress, which the agency suggests is lacking in Section 202(a).
Factual and evidentiary bases for proposed rescission
Supplementing EPA’s legal rationale for rescinding the Endangerment Finding, the proposed rule also criticizes the prior factual and scientific analysis and concludes that the Endangerment Finding was unreasonable, not adequately supported by contemporaneous empirical data or evidence, and contradicted by more recent data and climate trends.
Key components of EPA’s determination that the Endangerment Finding is not supported by the facts and evidence include:
- New evidence and data: EPA’s proposal would find that the scientific record, including recent data and studies, cast doubt on the prior analysis, including its assessment of uncertainties as well as forecasts and predictions underlying the Endangerment Finding.
- No “requisite technology” to control GHG emissions from vehicles: EPA’s proposal would also find that even reducing US GHG emissions from new motor vehicles and engines to zero “would not have a scientifically measurable impact on global GHG concentrations and climate trends.” Based on that determination, EPA would conclude there is no “requisite technology” (as required by CAA Section 202) to mitigate any endangerment to public health and welfare caused by global climate change.
- Restoring consumer choice: EPA proposes to conclude that existing GHG emission standards for new vehicles and engines would harm public health and welfare by increasing prices, decreasing consumer choice, and delaying replacement of older vehicles that are less safe and generate greater emissions of air pollutants.
EPA estimates that the proposed rule would save consumers and industry approximately $54 billion annually. The agency will accept public comments on the proposed rescission of the Endangerment Finding and repeal of vehicle and engine GHG emissions standards through September 15, 2025.
EPA has also scheduled a public hearing on the proposal for August 19–20, 2025. We anticipate this major regulatory action will be controversial and generate significant comments in support and opposition.
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