A Turning Point for Greenhouse Gas Emissions Regulation: EPA Seeks to Repeal its Endangerment Finding

On Aug. 1, 2025, the U.S. Environmental Protection Agency (EPA) initiated a major climate policy shift by proposing to rescind its 2009 Endangerment Finding, which has been the basis of many regulatory efforts to reduce greenhouse gas emissions from both mobile and stationary sources. The proposed rule, Reconsideration of 2009 Endangerment Finding and Greenhouse Gas Vehicle Standards, 90 Fed. Reg. 36288 (Aug. 1., 2025) (Reconsideration Proposal), also seeks to rescind all greenhouse gas emission standards for light-duty, medium duty, and heavy-duty vehicles and engines promulgated under section 202(a) of the Clean Air Act (CAA) and based on the Endangerment Finding. While the Reconsideration Proposal explicitly seeks to repeal existing vehicle emission standards, EPA signaled potential changes for other industries reliant on the Endangerment Finding, including oil and gas, power plants, and aircraft engine manufacturers. As the Agency re-examines its authority and the scientific basis for regulating greenhouse gases, businesses and policymakers should prepare for changes in regulatory direction and policy uncertainty.

Public Comment Deadline and Hearings

On Aug. 15, 2025, EPA extended the public comment period for the reconsideration of the endangerment finding to Sept. 22, 2025. Public hearing schedules are located on EPA's website.

Legal History and Regulatory Context of the Endangerment Finding (2007-2025)

In Massachusetts v. EPA, 549 U.S. 497 (2007), the U.S. Supreme Court found that greenhouse gases constitute an "air pollutant" under section 202(a) of the CAA and instructed the Agency to determine, under that section, whether greenhouse gas emissions "may reasonably be anticipated to endanger public health or welfare." In response, EPA issued the Endangerment Finding on Dec. 15, 2009, which defined "air pollution" under section 202(a) of the CAA to include a mix of six greenhouse gases-carbon dioxide, nitrous oxide, hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride. Endangerment and Cause or Contribute Findings for Greenhouse Gases Under Section 202(a) of the Clean Air Act, 74 Fed. Reg. 66494 (Dec. 15, 2009) (Endangerment Finding). EPA determined that, together, these six air pollutants contributed to global climate change, which was reasonably anticipated to endanger public health and welfare. Prior to the Endangerment Finding, EPA focused primarily on regulating air pollution that endangered public health and welfare through local or regional exposure (i.e., criteria and hazardous air pollutants). EPA relied upon the Endangerment Finding under Title II of the CAA to regulate greenhouse gas emissions from minor and major stationary sources under section 111 of the CAA-most notably in the electricity generation and oil and gas sectors.

EPA's Fluctuating Authority to Regulate Greenhouse Gas Emissions

In 2014, the U.S. Supreme Court rolled back some of EPA's expansion of greenhouse gas regulatory authority via the CAA's permitting provisions in Utility Air Regulatory Group v. EPA (UARG), 573 U.S. 302 (2014). This case evaluated EPA's authority to issue the "tailoring rule," under which EPA changed the major source permitting threshold for greenhouse gas emissions from 250 tons per year to 100,000 tons per year because the 250 tons per year threshold would subject thousands of additional and non-traditional sources to permitting requirements. The Court held that EPA could not require a source to obtain a permit under the CAA's Title V or Prevention of Significant Deterioration permitting provisions solely based on the source's potential to emit greenhouse gases. EPA published a proposed rule to implement the decision, but it was never finalized. The Agency then shifted its attention to regulating greenhouse gases across certain economic sectors under its CAA section 111 authority. EPA focused largely on the electricity generating sector, particularly coal-fired power plants, issuing the Clean Power Plan to curb greenhouse gas emissions from existing power plants under section 111(d). In West Virginia v. EPA, 597 U.S. 697 (2022), the U.S. Supreme Court struck down the Clean Power Plan, officially ushering in the "major questions doctrine." The Court held that EPA exceeded its authority by regulating emissions "beyond the facility fence line" based on a "generating shifting approach" (i.e., mandating a shift in electricity production from higher-emitting to lower-emitting facilities).

Weeks after the West Virginia decision, Congress passed the Inflation Reduction Act (IRA), which added seven new sections to the CAA and emphasized the CAA's ability to regulate greenhouse gas emissions. The IRA also allocated federal funding for renewable energy projects, subsidies for electric vehicles and electric vehicle charging stations, energy efficiency projects, investments in carbon capture technology, and other greenhouse gas emissions-related policy initiatives. The new CAA provisions required EPA to establish zero emission regulations for heavy duty vehicles, regulate to reduce emissions from the electricity generation and oil and gas industries, provide environmental justice grants, and support state and local climate plans. On July 4, 2025, the One Big Beautiful Bill Act, Pub. L. No. 119-21, 139 Stat. 72 (2025), clawed back some of the IRA's provisions.

Regulations that Rely on the 2009 Endangerment Finding

Since 2010, EPA, at times in conjunction with other federal agencies, has issued numerous greenhouse gas standards for mobile and stationary sources of emissions, including but not limited to:

• Mandatory Reporting of Greenhouse Gases, 74 Fed. Reg. 56460 (Oct. 30, 2009).
• Light-Duty Vehicle Greenhouse Gas Emission Standards and Corporate Average Fuel Economy Standards, 70 Fed. Reg. 25324 (May 7, 2010).
• Oil and Natural Gas Sector: Emission Standards for New, Reconstructed, and Modified Sources, 81 Fed. Reg. 35824 (June 3, 2016).
• The Safer Affordable Fuel-Efficient (SAFE) Vehicles Rule for Model Years 2021-2026 Passenger Cars and Light Trucks, 85 Fed. Reg. 24174 (April 30, 2020).
• Oil and Natural Gas Sector: Emission Standards for New, Reconstructed, and Modified Sources Review [known as the "policy amendments"], 85 Fed. Reg. 57018 (Aug. 14, 2020).
• Emission Standards for New, Reconstructed, and Modified Sources: Oil and Natural Gas Sector Reconsideration [known as the "technical amendments"], 85 Fed. Reg. 57398 (Sept. 15, 2020).
• Revised 2023 and Later Model Year Light Duty Vehicle Greenhouse Gas Emission Standards, 86 Fed. Reg. 74434 (Dec. 30, 2021).
• Standards for Performance for New, Reconstructed, and Modified Sources and Emission Guidelines for Existing Sources: Oil and Natural Gas Sector Climate Review, 89 Fed. Reg. 16820 (March 8, 2024).
• Multi-Pollutant Emissions Standards for Model Years 2027 and Later Light Duty and Medium Duty Vehicles, 89 Fed. Reg. 27842 (April 18, 2024).
• New Source Performance Standards for Greenhouse Gas Emission from New, Modified, and Reconstructed Fossil Fuel-Fired Electric Generating Units; Emission Guidelines for GHG from Existing Fossil-Fuel Fired Electric Generating Units and Repeal of the Affordable Clean Energy Rule, 89 Fed. Reg. 39798 (May 9, 2024).
• Greenhouse Gas Reporting Rule: Revisions and Confidentiality Determinations for Petroleum and Natural Gas Systems, 89 Fed. Reg. 42062 (May 14, 2024).
• New Source Performance Standards for Greenhouse Gas Emissions from New, Modified, and Reconstructed Fossil Fuel-Fired Electric Generating Units; Emission Guidelines for Greenhouse Gas Emissions from Existing Fossil Fuel-Fired Electric Generating Units; and Repeal of the Affordable Clean Energy Rule, 89 Fed. Reg. 55521 (July 5, 2024).
• Waste Emissions Charge for Petroleum and Natural Gas Systems: Procedures for Facilitating Compliance, Including Netting and Exemptions, 89 Fed. Reg. 91094 (Nov. 18, 2024) (Congress directed EPA to remove the amendments to 40 C.F.R. Parts 98.3 and 98.4. Parts 98.3 and 98.4 via a Congressional Review Act resolution, see 90 Fed. Reg. 21225 (May 19, 2025)).
• Repeal of Greenhouse Gas Emissions Standards for Fossil-Fuel Fired Electric Generating Units, 90 Fed. Reg. 25752 (June 17, 2025).
• Reconsideration of the Greenhouse Gas Reporting Program, publication pending (Sept. 12, 2025).
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  EPA's Reconsideration of the Endangerment Finding

  The Reconsideration Proposal centers on EPA's changing legal and policy viewpoints regarding whether the CAA provides the Agency with clear and sufficient authority to regulate greenhouse gas emissions from vehicles and engines. The Agency argues that only after post-2009 U.S. Supreme Court decisions-namely Loper Bright Enterprises v. Raimondo, 603 U.S. 369 (2024), West Virginia v. EPA, Michigan v. EPA, 576 U.S. 743 (2015), and UARG-did it receive adequate legal guidance as to the scope of its greenhouse gas regulatory authority under the CAA. Fundamentally, the Reconsideration Proposal asserts that the rules that flowed from the 2009 Endangerment Finding created broad impacts across industries and markets without clear Congressional intent and, therefore, EPA lacked sufficient authority to adopt them.

  In the UARG decision overturning the tailoring rule, the U.S. Supreme Court held that the term "air pollutant" was not intended to have the same meaning across all CAA sections and, more specifically, that "air pollutants" under the Prevention of Significant Deterioration permitting regime did not include greenhouse gases as it would render the program "unworkable as written." Relying on this decision, the Reconsideration Proposal concludes the term "air pollutant" under CAA section 202(a) does not authorize regulation of greenhouse gas emissions from other sectors, including stationary sources. The Reconsideration Proposal also forecasts that, under Loper Bright, a court would find the term "air pollution" under CAA section 202(a) is best read in the context of local or regional exposure to dangerous air pollution consistent with EPA's longstanding practice before 2009 and should not be construed more broadly in relation to global climate change.

  The Reconsideration Proposal also concludes that the "major questions" doctrine announced in West Virginia (2024) applies to the 2009 Endangerment Finding. EPA asserts "the global climate change concerns addressed by that action and the mandatory duty to regulate triggered by that action, present a major question of undeniable political and economic significance." Applying the doctrine, EPA contends that prior actions regulating carbon dioxide and other greenhouse gas emissions from motor vehicles has mandated a shift from gasoline powered engines to electric vehicles-precisely the type of significant, pollution-shifting activity the Court struck down in West Virginia.

  In addition to EPA's new proposed legal interpretations, the Reconsideration Proposal advances secondary, alternative technical rationales for overturning the Endangerment Finding. These include a proposed finding that prior scientific studies EPA relied on are now undermined by recent developments. The Reconsideration Proposal notes that "global GHG concentrations in the upper atmosphere have continued to rise, driven primarily by increased emissions from foreign sources, all without producing the degree of adverse impacts to public health and welfare in the United States that EPA anticipated in the 2009 Endangerment Finding." EPA leans heavily on a recent Department of Energy study and international climate assessments to determine that the scientific basis for the Endangerment Finding is weaker than initially believed. See U.S. Department of Energy, Climate Working Group, A Critical Review of Impacts of Greenhouse Gas Emission on the U.S. Climate (July 23, 2025) (cited in the Reconsideration Proposal as "Impacts of Carbon Dioxide Emissions on the U.S. Climate"). Alternatively, EPA also proposes to find there is no "requisite technology" for light-duty, medium-duty, and heavy-duty vehicle emission controls because reducing emissions from such vehicles to zero would not measurably impact greenhouse gas concentrations or the rate of global climate change. According to the Reconsideration Proposal, any of these alternative rationales would independently support rescission of the Endangerment Finding and the greenhouse gas vehicle standards.

  Implications of EPA's Reconsideration Proposal

  Many of EPA's greenhouse gas emissions control regulations rely on the Endangerment Finding. These regulations also control criteria pollutant emissions, such as ozone precursors from oil and gas operations and passenger vehicles. If finalized, the Reconsideration Proposal would not affect the rules and regulations for criteria pollutants. For now, the Reconsideration Proposal only seeks to rescind the vehicle standards and indicates that the Agency will address in separate rulemakings whether and how rescission of the Endangerment Finding affects other sectors, including any potential changes to Corporate Average Fuel Economy (CAFE) standards. However, the impacts may not remain narrow. For example, in June, EPA proposed to repeal greenhouse gas standards for fossil fuel-fired power plants, applying much of the same case law and legal rationale as in the Reconsideration Proposal. And in July, the day before issuing the Reconsideration Proposal, EPA extended numerous deadlines for oil and gas operators subject to the subparts OOOOb and OOOOc of the New Source Performance Standards, which control methane emissions from sector, as well as criterial pollutants. These actions portend other changes to how (or if) EPA regulates greenhouse gases from various stationary sources in other economic sectors. The timing, scope, and breadth of those efforts, however, is uncertain. Moreover, there may be accelerated state and local efforts to address greenhouse gas emissions, which may impact economic and project development in those jurisdictions as California, Colorado, and other similarly situated states have experienced. Finally, there are companies that have already embarked on material greenhouse gas reduction efforts and goals that may prefer some level of greenhouse gas regulation remain in place to ensure their investments are not rendered obsolete.

  In the near term, the removal of greenhouse gas emission requirements from existing rules separate from the Reconsideration Proposal would be time consuming and subject to legal challenge by states, environmental groups, and potentially certain industries. The regulated community should also be aware that if the courts reverse EPA's recission of the Endangerment Finding, many of the current greenhouse gas regulations may "spring back" into place. The sum of these events appears to be regulatory uncertainty and instability for some time. More than ever, it will be critical for companies across all sectors to closely monitor all the interconnected EPA actions in this space and consider how they may affect both short- and long-term greenhouse gas and climate change strategies.