The Environmental Protection Agency (EPA) recently published its heavily anticipated proposal to revoke its 2009 determination under section 202(a) of the Clean Air Act (CAA) that greenhouse gases (GHG) "cause, or contribute to, air pollution which may reasonably be anticipated to endanger public health or welfare." That "endangerment finding" forms the legal basis for EPA to regulate GHG emissions from "any class or classes of new motor vehicles or new motor vehicle engines"—cars, trucks, buses, etc. This proposal, which is part of the holistic effort by the current administration to deregulate GHGs,1 was touted by EPA Administrator Lee Zeldin as "the largest deregulatory action in the history of America."
From a legal perspective, EPA's revocation of the endangerment finding is unprecedented, leading to uncharted territory that courts will have to ultimately navigate. The proposed revocation has elicited strong reactions across a broad range of interested parties. While some conservative groups are applauding the effort, officials in blue states and scientific and environmental groups have voiced loud concerns. Several environmental groups have already announced intentions to commence legal actions challenging the rule once finalized. Indeed, on August 12, 2025, a collateral challenge was filed by the Environmental Defense Fund and Union of Concerned Scientists challenging the validity of the Department of Energy's 2025 Climate Working Group (CWG) and its Draft Report, upon which the EPA relied to justify its reversal of the endangerment finding. Businesses with cross-border operations must determine how to react to the proposal, given the inherent conflicts with laws and regulations in other jurisdictions. Additionally, many of these businesses will need to rationalize any behavioral changes with their decades-long recognition of climate change risk and commitments to mitigate impacts associated with climate change. Many may shy away from engaging EPA in this debate to avoid appearing at odds with the administration.
EPA's Arguments for Revoking the Endangerment Finding
Statutory Authority
In its proposal, EPA argues that section 202(a) of the CAA does not "authorize the EPA to prescribe emission standards to address global climate concerns." Instead, EPA asserts that the statute's best interpretation—a nod to the Supreme Court's 2024 Loper Bright decision, which eliminated the Court's automatic deference to agencies' statutory interpretations—authorizes EPA to regulate air pollutants that "cause or contribute to air pollution that itself endangers public health and welfare through local or regional exposure" (emphasis added). EPA substituted the emphasized language for the CAA's express terms, "which may reasonably be anticipated to endanger public health or welfare." Reading these additional gatekeeping parameters (e.g., "itself" and "local and regional exposure"), may unintentionally expose EPA itself to challenges under Loper as the agency seeking to impermissibly stretch the statute to fit a policy purpose.
EPA's current proposal also raises several arguments regarding the review process undertaken by EPA in 2009 to arrive at the endangerment finding. According to EPA, the 2009 finding failed to establish that GHGs directly cause public health or welfare impacts and it improperly concluded that GHGs "cause, or contribute to, dangerous air pollution that causes, or contributes to, endangerment of public health or welfare"—a "mental leap" that is inconsistent with the statutory authority. One could argue that EPA's proposed analysis may itself take a mental leap by disregarding or too narrowly construing the meaning of "contribute" and ignoring the statutory parameter of "reasonably be anticipated to endanger." Relatedly, and apparently in another attempt to comport with recent Supreme Court decisions, EPA asserts that it lacks authority to regulate GHG emissions under the major questions doctrine, which requires clear congressional authority for agencies to act on major questions of policy. In all, Supreme Court precedent in Massachusetts v. EPA and the express language of section 202(a), combined with the tomes of science and data related to impacts of climate change to public health and welfare in the United States that will be put forth into the administrative record by academics, non-governmental organizations (NGOs) and many businesses, may greatly impede EPA's ability to defend the revocation of the endangerment finding. The composition of the Supreme Court is different now than it was in 2007 when Massachusetts v. EPA was decided, with six Justices now comprising what is generally viewed as a conservative majority. The Court has, in recent years, made clear that stare decisis is an important, but not inviolable principle, and that it is willing to revisit (and in some cases overrule entirely) its own precedential authority,2 leaving the Court's future treatment of Massachusetts uncertain.
The Science
EPA argues that, even if its statutory authority arguments fail and consideration of global climate concerns for the 2009 finding was therefore appropriate, in the alternative the finding should be revoked on the basis that the agency in 2009 had "unreasonably applied the statutory standard for regulation to the scientific record." Put differently, EPA argues that the endangerment finding was flawed scientifically. The proposed rule, emphasizing the discretion afforded under the statute, concludes that "in an exercise of discretionary judgment, . . . there is insufficient reliable information to retain the conclusion that GHG emissions from new motor vehicles and engines in the United States cause or contribute to endangerment to public health and welfare in the form of global climate change."3 It further asserts that the "Administrator would exercise his discretionary judgment differently today in light of intervening legal and scientific developments that appear to undermine the assumptions, methodologies, and conclusions of the Endangerment Finding." In defending this statement, EPA relies primarily on the Department of Energy's CWG Draft Report, which has generated significant criticism across the scientific community. The CWG report, as well as EPA's reliance on it for purposes of revoking the endangerment finding, have already been challenged in court.
In EPA's analysis, rather than arguing that the science outright contradicts that GHGs contribute to air pollution that may reasonably be anticipated to endanger public health or welfare, the agency appears to rely on scientific uncertainty around the impacts of climate change—a strategy that failed when argued in Massachusetts v. EPA. EPA, using often siloed scientific data primarily from the CWG report, argues that in hindsight, the global public health and welfare impacts identified in the 2009 finding turned out to be overblown when compared to what has happened in the United States. For example, the proposed rule notes that the 2009 finding identified public health and welfare impacts from rising global average sea levels, but that during the intervening period since 2009, the aggregate sea level has risen in some U.S. localities but declined in others. Additionally, in arguing that the 2009 finding was "unduly pessimistic in attributing health risks from heat waves to increases in global temperature," EPA cites the CWG report to conclude that "the data suggest that domestic temperatures peaked in the 1930s and have remained more or less stable, in relative terms, since those highs." Going one step further, EPA asserts that because "mortality risk from cold temperatures remains by far the greater threat to public health in the United States and around the world at the aggregate level" compared to mortality from hot temperatures, rises in global temperature, and "the balance of climate change as a whole," provide net benefits.
The proposed rule seeks public comment in all respects, including whether "there is a strong enough scientific record to support an affirmative finding that GHG emissions from section 202(a) sources cause or contribute to air pollution which may reasonably be anticipated to endanger public health or welfare." Ironically, the proposal came on a day that more than 150 million Americans from the central United States to the East Coast were under a Level 3 or Level 4 heat risk (on a scale of 4). Indiana, where Zeldin officially announced the proposal, was under an extreme heat warning with temperatures expected to feel like 105°F. It also comes in the face of the recent International Court of Justice (ICJ) landmark advisory opinion holding that United Nations nation-states are obligated to protect their citizens from the "urgent and existential threat" of climate change.
In justifying the proposed rule, EPA emphasizes the issue of statutory discretion afforded to the administrator in making this finding (i.e., that the EPA administrator must set standards for "the emission of any air pollutant . . . which in his judgment cause, or contribute to, air pollution which may reasonably be anticipated to endanger public health or welfare" (emphasis added)). The Supreme Court addressed this language in Massachusetts v. EPA, finding that, although the language at issue vests the agency with statutory discretion, that discretion "is not a roving license to ignore the statutory text. It is but a direction to exercise discretion within defined statutory limits." Given the Court's position in Massachusetts v. EPA, as well as the claims questioning the scientific veracity of the CWG report, EPA's reliance on such statutory discretion will undoubtedly be scrutinized, with stakeholders expected to argue that EPA's exercise of such discretion does not permit it to cherry-pick favorable scientific data to support its desired outcome, but rather requires the administrator exercise discretion upon review of a complete record.
What Does This Mean for the Future of U.S. Climate Regulation?
The proposal has already received over 70,000 comments and undoubtedly will face a continuing onslaught of public comments from various stakeholders, including environmental organizations, industry groups and concerned citizens. If finalized, the rule will be subjected to legal challenges questioning the validity of EPA's arguments and its apparent determination that there is no need or authority to regulate GHGs. While EPA faces a long road ahead before revocation of the endangerment finding could become effective, if the courts ultimately uphold a final rule, this EPA may feel empowered to revoke swiftly the vast majority of federal regulations governing GHG emissions.
Although EPA states that withdrawing the endangerment finding will resolve regulatory uncertainty that has existed since being implemented in 2009, the rule itself acknowledges that the move is apt to exacerbate regulatory uncertainty. For instance, if the revocation is upheld based on scientific grounds, then what would stop a future administration from reinstating the finding based on the scientific consensus regarding the public health and welfare impacts of GHGs at that time?4 On the other hand, if the revocation is upheld based on the statutory discretion afforded to the EPA administrator, that discretion could similarly be exercised by a future administration to support reinstating the finding.5 Thus, EPA may be introducing a larger and more volatile regulatory pendulum than the one it faced under the 2009 finding.
In the meantime, the proposed revocation, follows a series of steps—the withdrawal from the Paris Agreement, the proposed finding of no endangerment related to U.S. power plant emissions, and orders to keep coal plants operational—that could have more direct impacts now, for example, by making it more difficult or costly for states to combat climate change and individual entities to meet their previously announced sustainability goals. In addition, the proposal adds complexity for manufacturers of motor vehicles or motor vehicle engines that have invested significantly to improve GHG performance and comply with federal GHG regulations or that operate in multiple jurisdictions with regulatory reporting and disclosure regimes that conflict with the administration's deregulatory approach to climate and environmental issues.
EPA has extended the public comment period for the proposed rule to September 22, 2025. A four-day public hearing on the proposal is underway this week, and Akin will continue to monitor developments closely. Akin regularly advises its clients on these and other complex matters, and we are available to assist our clients who may wish to participate in the public comment process with respect to the proposed rule.
Footnotes
1. Other actions in this effort include EPA's proposal in June to revoke the endangerment finding for GHG emissions from stationary sources under section 111(b) of the CAA and to eliminate all regulatory drivers and financial incentives for electric vehicles.
2. See, e.g., Loper Bright Enters. v. Raimondo, 600 U.S. 369 (2024) (overturning Chevron deference to agency interpretation of their statutory authority); Dobbs v. Jackson Women's Health Org., 597 U.S. 215 (2022) (overturning Roe v. Wade); Edwards v. Vannoy, 583 U.S. 976 (2021) (overturning the ability of criminal defendants to argue that consequential new rules of criminal procedure apply retroactively).
3. It should be noted that this determination is inconsistent with findings by the broader scientific community, including the most recent Intergovernmental Panel on Climate Change (IPCC) Report, which the EPA claims to have assessed.
4. Even EPA seems to concede this point, noting "[t]he bases for repeal proposed in this action would not foreclose us from regulating CO2, methane, NOX, HFCs, PFCs, or SF6 emissions from new motor vehicles or engines if the Administrator determines that one or more of those gases meet the requirements for regulation under CAA section 202(a)."
5. This point, too, is apparently acknowledged by EPA, given its assertion that the "Administrator would exercise his discretionary judgment differently today" based on the referenced scientific and legal developments.
The content of this article is intended to provide a general guide to the subject matter. Specialist advice should be sought about your specific circumstances.
