On August 1, 2025, the U.S. Environmental Protection Agency (EPA) issued a proposed rule to reconsider the 2009 Greenhouse Gas (GHG) Endangerment Finding (Endangerment Finding) and proposed to repeal all GHG emission standards for light-duty, medium-duty, and heavy-duty vehicles and engines promulgated under Section 202(a) of the Clean Air Act (CAA). See Reconsideration of 2009 Endangerment Finding and Greenhouse Gas Vehicle Standards, 90 Fed. Reg. 36,288 (Aug. 1, 2025) (Proposed Rule). EPA’s primary basis for the Proposed Rule is that EPA lacks statutory authority under CAA Section 202(a) to prescribe emission standards to address global climate change concerns in light of more recent Supreme Court decisions, and it also advances several alternative bases for the action. The Proposed Rule does not have any immediate impact on either the car manufacturing industry or any other industry, as it is not yet final. However, if finalized, the Proposed Rule would eliminate existing federal GHG requirements for new motor vehicles and engines, including compliance, reporting and certification obligations for manufacturers, importers, and regulated entities. Notably, the Proposed Rule does not impact the CAA provisions that support EPA’s fuel economy standards, Corporate Average Fuel Economy (CAFE) testing, and emission standards for criteria pollutants and hazardous air pollutants for motor vehicles and engines.
Clients should attentively track this rulemaking process, as EPA acknowledges that it has relied on the Endangerment Finding to promulgate regulations under other CAA provisions, and that it “ha[s] initiated or intend[s] to initiate separate rulemakings that will address any overlapping issues.” Id. at 36,298.
The Proposed Rule includes several primary and alternative legal rationales for rescinding the Endangerment Finding and GHG emission standards for motor vehicles and engines, which are detailed below.
Lack of Authority under CAA Section 202(a). EPA’s primary argument for rescinding the Endangerment Finding is that it does not have the statutory authority under CAA Section 202(a) to prescribe emission standards to address global climate change concerns. CAA Section 202(a) allows EPA to prescribe regulations for the emission of any air pollutant from engines that “cause, or contribute to, air pollution which may reasonably be anticipated to endanger public health or welfare.” Previously, EPA interpreted statutory silence in CAA Section 202(a) regarding global climate change impacts to public health and welfare to mean that it had the discretion to prescribe GHG standards for motor vehicles and engines. Id. at 36,299. However, EPA now interprets CAA Section 202(a) as only authorizing it to identify and regulate air pollutants that cause or contribute to air pollution that endangers public health and welfare “through local and regional exposures.” Id. at 36,300 (emphasis added). In doing so, EPA intends to distinguish “air pollution that impacts public health and welfare by its presence in the ambient air [(i.e., on a localized level)] from ‘air pollution’ consisting of six ‘well-mixed’ GHGs that, as conceptualized in the Endangerment Finding, impacts public health and welfare indirectly [(i.e., on a global level)] and not by its mere presence in the ambient air.” Id.
EPA relies on the recent Supreme Court decisions in Loper Bright Enterprises v. Raimondo, 603 U.S. 369 (2024), West Virginia v. EPA, 597 U.S. 697 (2022), and Utility Air Regulatory Group v. EPA, 573 U.S. 302 (2014) to support this change in interpretation. EPA reasons that the major questions doctrine set forth in West Virginia v. EPA and the overturning of Chevron deference in Loper Bright have led it to interpret the statutory silence in CAA Section 202(a) as a lack of clear authorization from Congress to regulate GHGs from motor vehicles and engines to address global climate change concerns. Id. at 36,305–36,306. EPA further explains that its change in interpretation is consistent with the “decades-long” implementation of CAA Section 202(a) and this recent Supreme Court precedent. Id. at 36,300.
Finally, EPA contends that it misinterpreted the Supreme Court’s decision in Massachusetts v. EPA, 549 U.S. 497 (2007), which vacated EPA’s denial of a petition for rulemaking to regulate carbon dioxide and GHGs from motor vehicles and led to EPA’s Endangerment Finding in 2009. Id. at 36,302. The Proposed Rule explains that following Massachusetts v. EPA, EPA erroneously interpreted the decision to mean that it was required to find that GHGs are subject to regulation under CAA Section 202(a). Id. The Proposed Rule explains that while Massachusetts v. EPA held that GHGs could be considered “air pollutants” under the CAA’s definition of “air pollutants” in Section 302(g), and therefore subject to regulation under CAA Section 202(a), subsequent Supreme Court decisions have clarified that the Massachusetts v. EPA decision did not require EPA to regulate GHGs under CAA Section 202(a) or to make the Endangerment Finding. Id.
Unreasonable Application of Statutory Standards to the Scientific Record. As an alternative, EPA argues that even if CAA Section 202(a) authorized EPA to address GHG emissions based on global climate change impacts, EPA unreasonably exercised that authority by severing the regulatory action into separate “endangerment” and standard-setting proceedings. Id. By severing the proceedings, EPA failed to consider adaptation to climate change, mitigation of GHG emissions, and costs when it issued the Endangerment Finding and standards in separate proceedings. Id. at 36,303. EPA now asserts that CAA Section 202(a) is an “integrated regulatory provision” that requires EPA to make an endangerment finding and prescribe emissions standards to alleviate those impacts in the same proceeding. Id. at 36,302–36,304.
Scientific Uncertainty and New Evidence. As another alternative, EPA asserts that the Endangerment Finding acknowledged “significant uncertainties related to climate change.” Id. at 36,308–36,310. And that new scientific evidence indicates that the Endangerment Finding was “unduly pessimistic” with respect to climate change and its impacts on public health and welfare. Id.
Lack of “Requisite Technology” to Address Identified Concerns. As a third alternative, EPA asserts that there is no “requisite technology” for light-, medium-, and heavy-duty vehicles that can meaningfully address global concentrations of GHGs in the upper atmosphere. Id. at 36,311. Moreover, “the impact of reducing all GHG emissions from motor vehicles and motor vehicle engines to zero would not result in a measurable impact on trends in climate change.” Id. at 36,312. Accordingly, the Proposed Rule concludes that this fact alone serves as an independent and sufficient basis for repealing the relevant GHG emission standards, because even if GHGs from motor vehicles and engines were eliminated, such reductions would not have a meaningful impact on the dangers associated with global climate change that were identified in the Endangerment Finding. Id.
The Proposed Rule signals that the second Trump Administration’s EPA is taking aggressive steps to fulfill its deregulatory promises made in a March 12, 2025, press release titled “EPA Launches Biggest Deregulatory Action in U.S. History.” In addition, the Proposed Rule appears to, at least initially, satisfy President Trump’s directive in Executive Order No. 14154 “Unleashing American Energy” for the EPA Administrator to provide recommendations to the Office of Management and Budget Director on the “legality and continuing applicability” of EPA’s prior Endangerment Finding, and attempt to further President Trump’s campaign promises to reduce the cost of living by “giving Americans the ability to purchase a safe and affordable car . . . while decreasing the cost of living on all products that trucks deliver.” See Proposed Rule Press Release (July 29, 2025).
While the Proposed Rule is specific to the GHG emission standards for vehicles and engines, EPA is “reconsidering additional endangerment findings and GHG emission standards issued under distinct provisions of the CAA in separate rulemakings.” 90 Fed. Reg. at 36,293. Therefore, EPA may propose additional rules in the coming months or years to rescind or reconsider GHG regulations for other regulated industries.
EPA is accepting public comment on the Proposed Rule until September 15, 2025, and plans to hold public hearings on August 19–20, 2025. See Public Hearing for Reconsideration of 2009 Endangerment Finding and Greenhouse Gas Vehicle Standards, 90 Fed. Reg. 36,125 (Aug. 1, 2025). If you have any questions about EPA’s Proposed Rule or how to participate in this or future EPA rulemakings, please contact John Jacus, Melanie Granberg, Cole Killion, or Natalie Boldt.