Key Takeaways
- What Happened? On July 29, 2025, the U.S. Environmental Protection Agency (EPA) published a proposed rule to rescind the 2009 Greenhouse Gas (GHG) Endangerment Finding ("Endangerment and Cause or Contribute Finding for Greenhouse Gases Under Section 202(a) of the Clean Air Act," 74 Fed. Reg. 66496 (Dec. 15, 2009)) (Endangerment Finding) and repeal all GHG emission standards for light-, medium-, and heavy-duty motor vehicles and engines under Clean Air Act (CAA) Section 202(a), 42 U.S.C. § 7521(a). The rule proposes to rescind only the Endangerment Finding under the CAA's mobile source provisions and not the separate endangerment findings that EPA has made with respect to stationary sources and aircraft engines, but it has potential implications for the latter findings as well.
- Who is Impacted? The Endangerment Finding was the prerequisite for all subsequent actions under the CAA that treat GHGs as regulated "pollutants." Accordingly, stakeholders include all industries subject to CAA regulations addressing climate change, including the automotive sector, utilities, and the oil and gas sector, as well industries that have developed products to address GHG emissions, such as electric vehicle manufacturers.
- What Should You Do? Stakeholders should carefully review the proposed rule and consider submitting comments to the docket (Docket ID No. EPA-HQ-OAR-2025-0194). Comments are due on or before September 15, 2025. EPA plans to conduct a virtual public hearing for the proposed rule on August 19 and 20, 2025, and EPA will share more information here. Notably, EPA requested comments on 27 identified aspects of the proposed rule.
Analysis and Key Elements of the Proposed Rule
The proposed rule would rescind the Endangerment Finding, which provided EPA the basis, for example, for regulating GHG emissions from new motor vehicles and engines. More specifically, the Endangerment Finding found that (1) six GHGs (carbon dioxide (CO2), methane, nitrous oxide (N2O), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF6)) were "air pollution" that may endanger public health and welfare, and (2) that GHG emissions from all potential classes of motor vehicles and engines contribute to elevated levels of GHGs and air pollution that endangers public health and welfare.
The proposed rule would also repeal all motor vehicle and engine GHG emission regulations because rescission of the Endangerment Finding would remove the basis and justification for these emission standards and the associated test procedures, averaging, banking, and trading requirements, reporting requirements, and fleet-average emission requirements (collectively, emission standards).
Similarly, EPA's recent proposal under Section 111 of the CAA to repeal GHG emission regulations for power plants identifies the separate endangerment finding for stationary sources as a "necessary predicate for regulation." That proposal, which EPA issued before the Agency's proposal to rescind the mobile source Endangerment Finding, would reinterpret Section 111 to require EPA to find that a category of emissions sources contributes significantly to climate change, and concludes that the U.S. fossil-fired generation fleet does not contribute significantly to climate change because it accounts for only a small percentage of global GHG emissions. If EPA's proposal to rescind the mobile source Endangerment Finding is adopted, it may undercut the rationale for regulating power plant GHG emissions as well as other CAA GHG regulations, depending on which of its proposed rationales EPA decides to include in its final rule.
Below, we discuss EPA's "multiple, independent alternative legal rationales" for rescinding the Endangerment Finding.
- The Endangerment Finding exceeded EPA's statutory
authority.
EPA's primary proposed basis for rescinding the Endangerment Finding is that CAA Section 202(a) does not authorize the Agency to issue GHG emission standards based on global climate change concerns in a stand-alone endangerment finding. More specifically, EPA asserts that "'air pollution' defined as 'six well-mixed' GHGs raising global climate change concerns that adversely impact a subset of regions globally" does not satisfy the standard—air pollution that threatens public health or welfare through local or regional exposure—under the best reading of Section 202(a).
EPA noted that following Massachusetts v. EPA, 549 U.S. 497 (2007), the Agency "assumed that statutory silence granted discretion to construe the scope of our authority and asserted or implied that the Supreme Court's decision in Massachusetts required us to read the statute as authorizing the regulation of GHG emissions in response to global climate change concerns." EPA explained how judicial decisions in the years since Massachusetts have provided additional clarity on agency discretion and the major questions doctrine. First, EPA explains that Loper Bright Enterprises v. Raimondo, 603 U.S. 369 (2024), overturned the longstanding doctrine of deference to agency statutory interpretation, "ruling that statutes 'have a single, best meaning' that is informed, but not dictated, by Executive Branch practice." EPA proposes that the best reading of Section 202(a), as informed by Loper Bright, is that Section 202(a) "does not authorize EPA to assert jurisdiction over GHG emissions based on global climate change concerns in a stand-alone endangerment finding." EPA also proposes that this reading of Section 202(a) is independently confirmed and strengthened by the major questions doctrine, and that the doctrine applies here and precludes EPA from asserting authority to regulate under Section 202(a) due to global climate change concerns. EPA notes that West Virginia v. EPA, 597 U.S. 697 (2022), built on Utility Air Regulatory Group v. EPA, 573 U.S. 302 (2014) and FDA v. Brown & Williamson Tobacco Corp., 529 U.S. 120 (2000), for the proposition that an agency needs more than "'a colorable textual basis' to assert authority to decide major questions of policy that Congress would generally reserve for itself."
- Alternatively, even if CAA Section
202(a) provided EPA with authority to issue GHG emission standards
for new motor vehicles and engines, EPA misapplied the statutory
standard to the scientific record in the Endangerment
Finding.
EPA believes that legal and scientific developments since Massachusetts undercut the Endangerment Finding's assumptions, methodologies, and conclusions. Concerns with the Endangerment Finding noted in the proposed rule include climate science uncertainties, reduced confidence in the reasonableness, accuracy, and reliability of the Endangerment Finding's assumptions and conclusions, the Endangerment Finding's inconsistent treatment of the nature and extent of the role of human action with respect to climate change, and the Endangerment Finding's failure to balance projected adverse climate impacts with potential benefits of increased GHG concentrations (particularly CO2 concentrations). Based on EPA's review of newer data and the stated concerns, the Agency proposes to find that there is insufficient reliable information to support the Endangerment Finding's conclusion that new motor vehicle and engine GHG emissions in the United States cause or contribute to the endangerment of public health or welfare in the form of global climate change.
- EPA provided several additional bases for repealing
vehicle and engine GHG standards.
In addition to the legal bases for rescinding the Endangerment Finding and, in turn, the basis for regulating GHG emissions from motor vehicles and engines, EPA proposes additional reasons for repealing the vehicle and engine GHG emission standards. EPA proposes that there is no "requisite technology" that meaningfully addresses (for light- and medium-duty motor vehicles) and addresses (for heavy-duty motor vehicles) the identified dangers of GHG air pollution. EPA reaches this proposed conclusion because reducing such vehicles' GHG emissions would not have a measurable impact on atmospheric GHG concentrations or global climate change. In addition, EPA proposes to find that GHG emissions standards may harm public welfare by reducing fleet turnover that improves air quality, safety, consumer choice, and economic opportunity.
Repeal of Motor Vehicle and Engine GHG Emission Standards
As noted above, EPA proposes to repeal all GHG emissions standards for motor vehicles and engines because, in the absence of the Endangerment Finding, there would be no basis for these regulations. EPA believes that any of the bases as mentioned above justifies repealing the vehicle and engine GHG emission standards. Accordingly, EPA proposes to repeal all GHG emission standards in the regulations found at 40 C.F.R. Parts 85, 86, 1036, and 1037, along with conforming revisions to unrelated emission standards for new motor vehicles and engines in the regulations found at 40 C.F.R. Parts 600 and 1039. EPA notes that this proposal is not revising emissions standards for criteria pollutants or air toxics. Further, EPA is not reopening or proposing to revise the regulations supporting the National Highway and Traffic Safety Administration's Corporate Average Fuel Economy (CAFE) standards or EPA's co-administration of the Energy Policy and Conservation Act of 1975 and the Energy Independence and Security Act of 2007.
Preemption
EPA takes the position that rescinding the Endangerment Finding and repealing the vehicle and engine GHG emissions standards will not impact federal preemption of new motor vehicle and engine emission standards. EPA notes that new motor vehicles and engines would remain subject to Title II of the CAA, which would preempt state or local standards related to controlling motor vehicle and engine emissions. EPA additionally notes that the CAA would preempt federal common-law claims related to GHG emissions because "'Congress delegated to EPA the decision whether and how to regulate' such emissions." (Am. Elec. Power Co. v. Connecticut, 564 U.S. 410, 426 (2011)). EPA goes on to state that the proposed rule would not prohibit EPA from regulating GHGs from new motor vehicles and engines if the Administrator determined that one or more of the six GHGs meet the Section 202 (a) requirements for regulation.
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