The Legal Foundation of U.S. Climate Regulation Is Under Attack: Two Petitions Filed After EPA Withdraws the Endangerment Finding

The Legal Foundation of Federal Climate Regulation Is Under Direct Attack in the D.C. Circuit

On February 18, 2026, the U.S. Environmental Protection Agency (EPA) published a final rule titled “Rescission of the Greenhouse Gas Endangerment Finding and Motor Vehicle Greenhouse Gas Emission Standards Under the Clean Air Act,” 91 Fed. Reg. 7686 (Feb. 18, 2026). With that action, the EPA formally withdrew the 2009 Greenhouse Gas Endangerment Finding, the determination that greenhouse gases “endanger public health and welfare” within the meaning of the Clean Air Act.

Within hours, litigation against the EPA's action began.

On the same day the rescission was published in the Federal Register, a coalition of climate and (public) health organizations filed a Petition for Review in the U.S. Court of Appeals for the District of Columbia Circuit under Clean Air Act § 307(b)(1), 42 U.S.C. § 7607(b)(1). A second petition for review was also filed by a group of youth, challenging the same final action. These filings marked the beginning of what is likely to become one of the most consequential administrative law battles in modern U.S. climate policy. The two legal challenges do not concern a single emissions standard. They go to the scientific and legal core of nearly all federal greenhouse gas regulation for the past fifteen years.

To understand the stakes, we will revisit what the Endangerment Finding is, how it emerged from Supreme Court precedent, and why rescinding it represents an attempt to unwind nearly two decades of regulatory framework.

The Endangerment Finding as the Legal Trigger for Climate Regulation

Section 202(a) of the Clean Air Act requires the EPA to regulate emissions from new motor vehicles or engines if it determines that a pollutant “causes, or contributes to, air pollution which may reasonably be anticipated to endanger public health or welfare.” This structure is mandatory, meaning that once the EPA makes an endangerment finding, regulation must follow.

The Supreme Court’s decision in Massachusetts v. EPA (2007) established that greenhouse gases qualify as "air pollutants" under the Clean Air Act. The Court rejected the EPA's earlier refusal to regulate carbon dioxide and instructed the EPA to ground its decision in the statutory endangerment standard and the scientific record. The EPA responded in 2009 with the Endangerment Finding. Drawing on assessments from the IPCC, the U.S. Global Change Research Program, and the National Research Council, the EPA concluded that six greenhouse gases, including carbon dioxide, endanger public health and welfare. That determination triggered regulation of motor vehicles and, through related Clean Air Act provisions, extended to stationary sources as well.

Since then, vehicle standards, power plant rules, methane regulations, and other measures have rested on that scientific and legal determination. Rescinding the Endangerment Finding therefore would entail the removal of the statutory trigger that activates federal greenhouse gas regulation in the first place.

EPA’s Authority to Reverse Course: Administrative Law Constraints

EPA’s rescission relies on the well-established principle that agencies may reconsider prior interpretations of a statute. Under the Administrative Procedure Act (APA), agency action is reviewed to ensure it is not “arbitrary, capricious, an abuse of discretion, or otherwise not in accordance with law,” 5 U.S.C. § 706(2)(A). The Supreme Court has made clear that agencies are not locked into earlier policies. In FCC v. Fox Television Stations, 556 U.S. 502 (2009), the Court held that an agency may change course so long as it “display[s] awareness that it is changing position” and provides a “reasoned explanation” for the new policy.

However, a policy shift is not immune to scrutiny. In Motor Vehicle Manufacturers Association v. State Farm Mutual Automobile Insurance Co., 463 U.S. 29 (1983), the Court emphasized that an agency must “examine the relevant data and articulate a satisfactory explanation for its action,” including a “rational connection between the facts found and the choice made.” When an agency rescinds a prior rule, it must grapple with the evidence underlying that earlier decision. And where regulated parties or states have structured their conduct in reliance on an existing regime, the agency must consider those reliance interests. See Department of Homeland Security v. Regents of the University of California, 591 U.S. 1 (2020).

The 2009 Endangerment Finding was not a mere policy preference. It was a scientific determination made pursuant to statutory language directing EPA to regulate if emissions “may reasonably be anticipated to endanger public health or welfare.” The D.C. Circuit upheld that determination against arbitrariness challenges in Coalition for Responsible Regulation v. EPA, 684 F.3d 102 (D.C. Cir. 2012), concluding that EPA had reasonably relied on the scientific record.

Against that backdrop, the central issue in the present litigation is not whether EPA may reconsider the Endangerment Finding. It is whether the Agency has satisfied the APA’s requirement of reasoned decision-making in withdrawing a scientific determination that once triggered mandatory regulation and that previously survived judicial review. That standard, rooted in § 706(2)(A) and shaped by State Farm, Fox, and Regents, will frame the D.C. Circuit’s analysis.

What Scientific Case Does EPA Make for Rescinding Endangerment?

The rescission does not deny that greenhouse gases are accumulating in the atmosphere or that they influence the climate system. Instead, as reflected in 91 Fed. Reg. 7686 (Feb. 18, 2026), EPA reinterprets how established climate science maps onto the statutory requirement that emissions "may reasonably be anticipated to endanger public health or welfare."

The rule narrows the analytical frame applied in 2009. Whereas the original finding relied on comprehensive assessments and treated long-term, cumulative, and global impacts as sufficient to satisfy the statutory threshold, the rescission places greater emphasis on the immediacy and directness of domestic harms. It questions whether projections of long-term global effects, even if supported by broad scientific consensus, satisfy the statutory standard in the absence of more proximate and localized impacts.

The rescission also assigns greater weight to scientific uncertainty. The 2009 Endangerment Finding acknowledged uncertainty in climate modeling but concluded that the weight of evidence supported a determination of risk. The new rule highlights variability in model projections, the complexities of event attribution, and regional differences in projected impacts. By foregrounding these features, the EPA suggests that predictive and probabilistic harms may not meet the "reasonably anticipated" threshold in the way previously understood.

In addition, EPA revisits causation and contribution. Although the Clean Air Act requires only that emissions "cause, or contribute to" endangering pollution, the rescission places renewed emphasis on the proportion of global emissions attributable to the United States and on the diffuse character of climate harms. While not disputing that U.S. emissions are part of the global total, the rule tightens the connection between domestic emissions and identifiable domestic impacts.

The dispute before the D.C. Circuit will not turn on whether climate change exists. It will turn on whether EPA has adequately justified its conclusion that a body of scientific evidence previously deemed sufficient to trigger regulation no longer meets the statutory threshold, particularly in light of a record that has expanded since 2009.

EPA's Legal Justification for Rescinding the Endangerment Finding

EPA’s rescission rests on its view that the Clean Air Act does not authorize regulation of greenhouse gases “in response to global climate change concerns.” In the rule’s summary, the Agency states that it is rescinding the 2009 findings “to effectuate the best reading of Clean Air Act (CAA) section 202(a)(1)” and that it “determines that CAA section 202(a)(1) does not authorize the Agency to prescribe emission standards in response to global climate change concerns”.

The EPA grounds that conclusion in its interpretation of the statutory terms “air pollution,” “cause,” “contribute,” and “reasonably be anticipated to endanger”. According to the EPA, the 2009 Endangerment Finding adopted an interpretation of these terms that exceeded what the statute properly allows. The rescission explains that the EPA now concludes “that the best reading of the statute does not authorize the EPA to prescribe GHG emission standards based on global climate change concerns” and further that “EPA erred in issuing the Endangerment Finding as a standalone action that severed the consideration of endangerment from the consideration of contribution and failed to engage with the standards that must issue when making such a finding”

The EPA also rejects the argument that the statutory references to “public health” and “welfare” confer broad discretion to regulate any pollution linked to climate change. In responding to commenters, the Agency states that it “disagrees that the references in CAA section 202(a)(1) to ‘public health’ and ‘welfare’ confer discretion broad enough to identify and regulate any form of air pollution, including in the form of global climate change concerns”. . It characterizes the broader reading adopted in 2009 as “inconsistent with ordinary principles of statutory interpretation” and as one that would “needlessly give rise to absurdity and nondelegation concerns".

The rescission further asserts that the EPA lacks statutory authority altogether under Section 202(a)(1) to regulate greenhouse gases in response to global climate change. The Agency states that it “concludes that it lacks statutory authority to regulate GHG emissions in response to global climate change concerns under CAA section 202(a)(1)”. Because of that conclusion, EPA explains that it cannot retain the Endangerment Finding based on asserted reliance interests.

The rule also invokes the Major Questions Doctrine as “corroborat[ing]” its statutory interpretation. The EPA states that it “further conclude[s], as proposed, that the major questions doctrine applies and bars the EPA from asserting the authority to decide the Nation’s policy response to global climate change concerns, including by attempting to force a shift to EVs, based on language authorizing the Agency to prescribe emission standards”. At the same time, the EPA maintains that rescission itself “does not trigger the major questions doctrine because an agency’s ability to reconsider, revise, and repeal prior actions is not an unheralded assertion of authority”. Finally, EPA asserts that greenhouse gas standards for new vehicles “do not impact in any material way the public health and welfare concerns identified in the Administrator’s prior findings in 2009”. On these “multiple and independent bases,” the Agency rescinds the 2009 Endangerment Finding and repeals the associated vehicle standards

Taken together, EPA’s legal argument is not simply that it may reconsider prior action. It is that, properly interpreted, Section 202(a)(1) never authorized regulation of greenhouse gases based on global climate change concerns in the first place, and that both statutory interpretation principles and the Major Questions Doctrine compel that conclusion.

Echoes of a Familiar Litigation Playbook

The EPA’s scientific reframing will sound familiar to observers of climate litigation over the past decade. Although this case arises under the Clean Air Act rather than tort or constitutional law, several of the themes mirror arguments long advanced by fossil fuel companies and governments defending against climate accountability claims.

In public nuisance and consumer protection suits against fossil fuel producers, defendants have consistently emphasized the global and cumulative nature of climate change. They argue that emissions are the product of countless actors ovekickr time and that no single entity’s conduct can be isolated as the proximate cause of particular injuries. Courts have repeatedly heard that climate harms are too diffuse and internationally distributed to satisfy traditional causation standards. EPA’s renewed focus on the proportion of U.S. emissions within the global total, and on the difficulty of linking domestic emissions to specific harms, reflects a similar tightening of the causal chain.

The emphasis on uncertainty follows a comparable pattern. Corporate defendants have often pointed to variability in climate model projections and limits in attribution science to argue that predictive harms are too speculative for liability. EPA’s rescission adopts a related posture by foregrounding uncertainty and suggesting that forward-looking risks may not satisfy the Clean Air Act’s “reasonably anticipated” threshold. Governments defending inadequate climate policies have likewise argued that domestic emissions represent only a fraction of global emissions and that unilateral regulatory action cannot alone prevent climate impacts. That reasoning resonates with EPA’s reframing of contribution and causation, even though the statutory context differs.

The key distinction, however, lies in the statute itself. The Clean Air Act requires only that emissions “cause, or contribute to” pollution that “may reasonably be anticipated” to endanger public health or welfare. That language was crafted to address cumulative and anticipatory harms. The D.C. Circuit will now have to determine whether EPA’s narrower reading effectively imports a more restrictive causation logic into a statute designed to operate on a precautionary basis.

Public Health at the Center of a Challenge

The first Petition for Review was filed by a coalition that includes the American Public Health Association, Alliance of Nurses for Healthy Environments, American Lung Association, Physicians for Social Responsibility, Environmental Defense Fund, Natural Resources Defense Council, Sierra Club, Union of Concerned Scientists, and numerous others. See Petition for Review, American Public Health Association et al. v. EPA, Case No. 26-1037 (D.C. Cir. Feb. 18, 2026). The petition explicitly seeks review of EPA’s rescission of the Endangerment Finding and related vehicle standards, published at 91 Fed. Reg. 7686 (Feb. 18, 2026)

This composition of petitioners is telling. The statutory phrase "endanger public health and welfare" is not incidental; it is the governing standard. By placing medical and public health organizations at the forefront, the litigation centers on concrete harms rather than abstract environmental injury.

The 2009 finding catalogued risks associated with rising temperatures, degraded air quality, vector-borne disease, extreme weather, and ecosystem disruption. Since then, the scientific literature linking climate change to heat-related mortality, respiratory disease, wildfire smoke exposure, and other health impacts has only expanded. Petitioners will therefore likely argue that withdrawing the finding in the face of a strengthened evidentiary record is inconsistent with the Administrative Procedure Act's requirement of reasoned decision-making.

The Broader Legal Architecture at Risk

The Endangerment Finding is woven into the broader regulatory fabric of the Clean Air Act. Vehicle standards triggered stationary source regulation through interconnected provisions. Subsequent climate rules have relied on its validity. If the D.C. Circuit invalidates the rescission, it will reaffirm the durability of agency scientific findings when grounded in robust evidence and affirmed by prior judicial review. If it upholds the rescission, it could open the door to significant retrenchment of federal climate authority.

The stakes are therefore systemic. The litigation is not about incremental regulatory adjustments but about whether the statutory gateway to climate regulation remains open.

For public health organizations, the case centers on the statutory commitment to protect health from anticipated harm. For administrative law scholars, it tests the limits of agency reversals in the face of strengthened scientific consensus. For climate policy, it determines whether the federal government retains the legal foundation to regulate greenhouse gas emissions under the Clean Air Act.

With the two petitions now filed, the D.C. Circuit will soon decide whether EPA may undo the scientific and legal determination that has underpinned U.S. climate regulation for nearly two decades. The outcome will surely reverberate across environmental law, public health governance, and the architecture of federal climate authority.

---

For those seeking deeper analysis of either of the two pending petitions, Climate Court subscribers receive full access to the filed Petitions for Review, procedural updates from the D.C. Circuit, and detailed breakdowns of the arguments as briefing unfolds.

We track developments in real time, including jurisdictional questions, motions practice, amicus participation, and any stay applications or emergency relief requests that may shape the trajectory of the case. As the litigation progresses, subscribers will also receive comparative analysis of how the rescission intersects with other federal and state climate cases. If you would like structured, legally rigorous updates on what may become the most consequential Clean Air Act case in a generation, you can subscribe to Climate Court for full access to our ongoing coverage.