Blog | EPA’s Proposed Endangerment Finding Revocation Purports to Limit Both Federal and State Climate Authority

By Amanda Lineberry, Senior Associate

On August 1, 2025, the U.S. Environmental Protection Agency (EPA) proposed to rescind the cornerstone 2009 Endangerment Finding that enables EPA to regulate greenhouse gases (GHGs) under the Clean Air Act (CAA). EPA’s Proposed Rule  re-interprets the CAA to restrict EPA’s authority to address global phenomena like climate change and offers both legal and factual arguments against regulating greenhouse gas emissions from motor vehicles, including assertions that U.S. vehicle emissions are not adequately tied to global climate change and that climate change is not as intense or harmful as the 2009 finding predicted, particularly when weighed against the costs of emissions regulations. The Proposed Rule relies, in part, on a July 29 report prepared for the U.S. Department of Energy (DOE) by a working group of five scientists skeptical of the prevailing scientific consensus about the impacts of climate change. A smaller but important piece of EPA’s Proposed Rule interprets the CAA to restrict not only federal authority to regulate greenhouse gases to address climate change but also states’ authority to do so through two distinct preemption arguments. This post explains the basics of EPA’s Proposed Rule and dives deeper into its CAA preemption arguments and what they mean for states. 

EPA’s Proposal to Rescind the Endangerment Finding

The Endangerment Finding is a legal prerequisite for regulating GHG emissions from motor vehicles under the CAA. Under Section 202 of the CAA, prior to initiating such regulation, EPA must first find that emissions will “cause, or contribute to, air pollution which may reasonably be anticipated to endanger public health or welfare." EPA issued the Endangerment Finding in 2009, after the Supreme Court’s landmark decision in Massachusetts v. EPA, which determined that the CAA allows EPA to regulate greenhouse gases because they qualify as air pollutants. In its 2009 finding, EPA concluded that six greenhouse gases endanger public health and welfare by contributing to climate change. Following this finding, in 2010 EPA began to regulate GHG emissions from motor vehicles. EPA’s new Proposed Rule includes three approaches for rescinding the 2009 Endangerment Finding and/or existing federal GHG emissions regulations for vehicles. 

EPA’s first and primary approach asserts that, despite the Massachusetts decision, EPA lacks statutory authority to regulate emissions contributing to climate change. This approach relies on a set of related arguments. First, EPA argues that “air pollution,” as that term is used in the CAA, extends only to pollution with local or regional effects, and does not extend to a global phenomenon such as climate change. Next, EPA asserts that the Clean Air Act requires an endangerment finding that is both pollutant- and source-specific before vehicle emissions can be regulated, and that the connection between GHG emissions from new motor vehicles in the US and the dangers of climate change is too attenuated to support such a finding. EPA also argues that the CAA does not authorize EPA to make an endangerment finding if the resulting regulations would be “futile as a means to address the identified dangers.” EPA asserts that recent Supreme Court decisions, including, among others, Loper Bright Enterprises v. Raimondo and West Virginia v. EPA, support its new reading of the CAA.

EPA puts forth two alternative approaches. In the first alternative approach, EPA asserts that, even if the CAA gives EPA the authority to address climate change, the 2009 Endangerment Finding’s scientific analysis was unreasonable and, relying on the climate working group’s report to DOE, claims that recent developments cast doubt on its conclusions. In the second alternative approach, EPA argues that, even if the 2009 Endangerment Finding is lawful, EPA’s vehicle emission standards would not have a “scientifically measurable impact” for mitigating climate change, which EPA asserts isn’t harming public health and welfare as much as previously believed, thus regulation of GHG emissions from vehicles is improper.

EPA’s two alternative approaches lean on the agency’s discretion to apply legal and regulatory standards to the facts at hand; subsequent administrations could reverse these determinations. But EPA’s first and primary approach—concluding that EPA lacks statutory authority to address climate change—would, if upheld, restrict future administrations from using CAA authority as a tool to regulate greenhouse gas emissions from vehicles to address climate change.

EPA’s Preemption Arguments

At the same time EPA proposes to eliminate the agency’s own ability to regulate climate-warming emissions, the Proposed Rule also addresses preemption of state action. The Proposed Rule makes three preemption arguments that are directly relevant to states seeking to reduce GHG emissions through their own programs. 

EPA’s first preemption interpretation is about “express preemption,” a type of federal preemption that occurs when a federal statute contains explicit language that overrides or displaces conflicting state or local laws. This argument rises and falls on an examination of the text of the statute at issue—in this case, the CAA.¹ 

EPA asserts that its proposal would leave in place CAA preemption of state emission standards for new vehicles because new vehicles “would remain subject to Title II of the CAA” even if no federal GHG standards were in place. The CAA Section 209(a) prohibits states from “adopt[ing] or attempt[ing] to enforce any standard relating to the control of emissions” from new motor vehicles or new motor vehicle engines covered by Title II of the CAA. Historically, California has obtained waivers from this preemption under CAA Section 209(b), which directs EPA to waive the preemption under certain conditions. According to a Congressional Research Service report, California has used those waivers more than 100 times to advance more stringent state-level standards for GHG emissions from vehicles, and 17 other states have adopted California’s standards.²

EPA’s second CAA preemption argument is premised on what is known as “field preemption.” Under this legal doctrine, federal regulation of a field is so pervasive that it implicitly either (1) displaces federal common law and/or (2) precludes states from imposing additional legal obligations in the same area. In its proposal, EPA argues that the CAA would continue to preempt Federal common-law claims–i.e., civil liability claims such as negligence, which can be brought by states or localities on behalf of their residents–for GHG emissions because “Congress delegated to EPA the decision whether and how to regulate” GHG emissions, citing American Electric Power Company v. Connecticut. This is because, according to EPA, the “bases for repeal proposed in this action would not foreclose” the agency from individually regulating emissions of one or more of the six GHGs considered in the 2009 Endangerment Finding from new vehicles if EPA “determines that one or more of those gases meet the requirements for regulation under” the CAA. In other words, EPA asserts that federal climate change torts still would be preempted by the CAA even though EPA now argues that the CAA does not authorize regulation of air pollution causing climate change.

In short, EPA argues that:

1. the federal government can’t regulate greenhouse gas emissions from vehicles to address climate change under the CAA; but, at the same time, 
2. the CAA still preempts state GHG emissions standards for vehicles as well as federal common-law claims seeking to mitigate GHG emissions.

What This Means for States

EPA’s proposed revocation of the 2009 Endangerment Finding interprets the CAA to be insufficient to enable federal regulation of GHG emissions from vehicles to address climate change but still sufficient enough to prevent state efforts to address those emissions through promulgating state vehicle emissions standards or bringing federal common law claims. States have been laboratories for new and innovative strategies to reduce planet-harming emissions in durable, cost-effective, and equitable ways. EPA is interpreting the CAA in the Proposed Rule to restrict not just its own action, but also to continue restricting states’ actions as well.

¹ EPA also asserts that the Proposed Rule would not affect federal preemption under EPCA of state fuel economy standards. EPCA’s preemption provision dictates that when a federal fuel economy standard is in effect, a state or locality “may not adopt or enforce a law or regulation related to fuel economy standards or average fuel economy standards” for vehicles covered by the federal standard. Some–including the Trump Administration during President Trump’s first term–have argued that this language separately preempts state GHG emissions standards for vehicles. At least two federal district courts have rejected similar arguments, however, concluding that EPCA did not displace the ability for California (and other states adopting its regulations) to obtain a CAA waiver for certain vehicle GHG emissions standards.

² With the support of the Trump Administration, Congress recently invalidated the Biden-era EPA’s approval of California’s waivers for its zero-emission car and truck sale standards by passing resolutions under the Congressional Review Act. Upon signing Congress’s resolutions, President Trump said “[p]reemption of these programs is essential to preserving the Constitution’s allocation of power both among the States and between the States and the Federal Government.” California and other states are challenging the waiver rescissions in court.