The EPA’s Unfolding Endangerment Finding Rescission Litigation
Coleman Hopkins
In the second year of President Trump’s second term, the Environmental Protection Agency (EPA) has again undertaken sweeping deregulatory actions,[1] many of which have already prompted judicial review.[2] One action in particular—the rescission of the EPA’s 2009 greenhouse gas Endangerment Finding—may prove especially consequential.[3] Promulgated through notice-and-comment rulemaking, the rule, if upheld, would significantly limit the scope and operation of the agency’s greenhouse gas regulatory framework.[4]
In late February, the American Public Health Association and several other climate- and public health-focused organizations filed a petition for review in the U.S. Court of Appeals for the District of Columbia Circuit challenging EPA Administrator Lee Zeldin’s final rule, Rescission of the Greenhouse Gas Endangerment Finding and Motor Vehicle Greenhouse Gas Emission Standards Under the Clean Air Act.[5] The rule removes a central feature of the Clean Air Act (CAA) regulatory framework governing greenhouse gas regulation—namely, the determination that greenhouse gas emissions pose a threat to public health and welfare and therefore fall within the scope of regulation under the Act.[6] If upheld, the rule will indeed constitute “the single largest deregulatory action in American history,” as President Trump has framed it.[7]
This blog proceeds in three parts. First, it briefly reviews the origin and legal significance of the Endangerment Finding. Second, it examines the emerging litigation in the D.C. Circuit and the administrative law questions likely to shape judicial review, including the scope of agency authority to revise prior scientific determinations. Third, it argues that the rescission sits uneasily alongside existing CAA doctrine and Supreme Court precedent,[8] raising substantial questions about the limits of agency discretion and making further judicial review all but inevitable.
1. Endangerment Finding: History, Meaning, & Regulatory Role
The “Endangerment Finding” issued in 2009 under 42 U.S.C. § 7521(a) identifies greenhouse gas emissions as posing a “threat to public health and welfare.”[9] It serves as the legal foundation for a range of regulations, including motor vehicle emissions standards.[10] This point must be underscored: the Endangerment Fining provides the statutory basis for EPA authority over greenhouse gas emissions from vehicles, which are among the largest sources of such emissions.[11]
The policy implications of this framework are contested. For President Trump, who has expressed skepticism regarding aspects of climate science[12] and maintains that the final rule “has nothing to do with public health,”[13] compliance with greenhouse gas emission standards imposes costs that car manufacturers pass on to consumers.[14] The Trump–Zeldin logic is straightforward: by removing the Endangerment Finding, the final rule will reduce costs for manufacturers, with downstream benefits for consumers.
For environmental groups, however, the Endangerment Finding is essential for addressing climate change and public health risks—critical national issues requiring federal regulatory solutions.[15] The final rule therefore removes a fundamental piece of the EPA’s larger regulatory scheme. Analogous to pulling out a foundation piece in a game of Jenga, without the Endangerment Finding, the EPA’s larger framework for addressing air pollution becomes unstable and perhaps fragile at best.
These contrasting views—on the existence of environmental and public health problems, the EPA’s role in addressing them, and the regulatory tradeoffs—proved irreconcilable and sparked the nascent litigation.
2. Understanding the Unfolding Rescission Litigation
The crux of the plaintiffs’ challenge is that the Trump Administration may not rescind a prior scientific determination without providing a reasoned explanation grounded in the administrative record. In the plaintiffs’ view, the Endangerment Finding—based on extensive scientific analysis upheld across administrations—cannot be discarded without a comparably rigorous reasoned justification. This argument draws on the logic of FCC v. Fox Television Stations, Inc, in which the Supreme Court held that agencies may change policy but must provide a reasoned explanation for doing so, particularly when prior policies have engendered reliance interests.[16]
The D.C. Circuit will determine whether the rescission satisfies the Fox Television framework.[17] The EPA is likely to argue that it has provided a sufficient explanation for its reversal. As part of that effort, the agency’s 2025 proposal cited a Department of Energy (DOE) report, assembled by a five-scientist panel,[18] that characterized the 2009 Endangerment Finding as “unduly pessimistic” and ultimately incorrect in its predictions.[19]
The EPA’s argument is, however, primarily legal in nature. It rests on an interpretation of 42 U.S.C. § 7521(a) under which the agency contends that greenhouse gas emissions do not fall within the statute’s scope.[20] As will be expanded on in the final Part below, this argument has implications for the Supreme Court and stare decisis.[21] If the court rejects the EPA’s position, the rule may be set aside as arbitrary and capricious; if not, it will be sustained.[22] Further appellate review is likely in either event.
In that sense, this case is not novel in doctrinal terms. Indeed, it can be understood as a recurring question about the policy priorities of a new administration and the constraints imposed by the Administrative Procedure Act (APA). What distinguishes the case is the significance of the underlying determination: the rescission of a foundational scientific finding that supports an entire regulatory regime. As a result, the agency’s evidentiary and explanatory showing will face careful judicial scrutiny.
This dynamic gives rise to a deeper procedure–substance tension. Courts reviewing agency action must evaluate whether the agency has provided a reasoned explanation, but in doing so, they may be required to engage with the underlying technical or scientific evidence. Where, as here, the agency’s explanation depends on scientific determinations, judicial review may approach the substance of those determinations, even if framed in procedural terms. This tension reflects a longstanding feature of arbitrary-and-capricious review, which requires reasoned decision-making without authorizing courts to substitute their own policy judgments.[23]
3. Massachusetts v. EPA Revisited and Future Concerns
The Endangerment Finding litigation points directly to a broader question: whether the EPA’s final rule effectively invites—if not compels—relitigation of Massachusetts v. EPA, which held that greenhouse gas emissions fall within the CAA’s definition of air pollutant and are therefore lawfully regulable.[24] That prospect is significant for at least three reasons.
First, it implicates the relationship between agency interpretation and judicial precedent. If the EPA’s interpretation of the CAA prevails, it would raise questions about the continued force of prior judicial constructions of the statute and could prompt calls for legislative revision. The issue may also become salient in future political and legislative debates.
Second, a ruling in favor of the EPA would substantially constrain the agency’s authority to regulate greenhouse gas emissions under the CAA, potentially limiting future administrations absent new congressional action. Such a development would shape the trajectory of environmental regulation and the balance of authority between Congress and the executive branch. Third, the litigation reflects broader shifts in administrative law, albeit with one caveat. The Court’s decision in Loper Bright Enterprises v. Raimondo recalibrated judicial deference to agency interpretations of statutes while emphasizing that its holding does not disturb prior precedents that relied on Chevron deference.[25] The Court thus struck a deliberate balance between doctrinal change and stare decisis. This case may test the limits of that balance, particularly where the Executive Branch seeks to effectively overturn longstanding Supreme Court precedent. This litigation may therefore provide insight into whether that balance will hold, or whether sustained challenges will erode it over time, with potential implications for the regulatory regimes that depend on it.
[1] Rescission of the Greenhouse Gas Endangerment Finding and Motor Vehicle Greenhouse Gas Emission Standards Under the Clean Air Act, 91 Fed. Reg. 7686 (Feb. 10, 2026); see also Final Rule: Rescission of the Greenhouse Gas Endangerment Finding, https://www.epa.gov/regulations-emissions-vehicles-and-engines/final-rule-rescission-greenhouse-gas-endangerment (last visited Mar. 13, 2026).
[2] See, e.g., Andrew Freedman, EPA Faces Multi-State Lawsuit Over Canceled Solar Grants, Axios (Oct. 17, 2025), https://www.axios.com/2025/10/17/lawsuit-trump-epa-states-solar-energy-grants-cancel.
[3] David Stout, Groups Sue Trump EPA Over Repeal of Climate Endangerment Finding, The Guardian (Feb. 18, 2026), https://www.theguardian.com/us-news/2026/feb/18/trump-epa-environment-climate-lawsuit.
[4] See 5 U.S.C. § 706(2)(A).
[5] Petition for Review of Final Rule: Rescission of the Greenhouse Gas Endangerment Finding and Motor Vehicle Greenhouse Gas Emission Standards Under the Clean Air Act, No. 26-xxxx (U.S. Ct. App. D.C. Cir. Feb. 25, 2026).
[6] Id.
[7] Matthew Daly, Groups Sue Trump’s EPA Over Repeal of Rule That Supported Climate Protections, PBS NewsHour (Feb. 18, 2026), https://www.pbs.org/newshour/politics/groups-sue-trumps-epa-over-repeal-of-rule-that-supported-climate-protections.
[8] See Massachusetts v. EPA, 549 U.S. 497 (2007) (holding EPA determinations regarding public health and welfare must rest on scientific findings, not policy reasons); see also Coalition for Responsible Regulation v. EPA, 684 F.3d 102 (D.C. Cir. 2012) (en banc) (upholding EPA’s 2009 endangerment finding under the APA).
[9] Endangerment and Cause or Contribute Findings for Greenhouse Gases Under Section 202(a) of the Clean Air Act, 74 Fed. Reg. 66,496 (Dec. 15, 2009).
[10] See, e.g., Carbon Pollution Emission Guidelines for Existing Stationary Sources: Electric Utility Generating Units, 80 Fed. Reg. 64,662 (Oct. 23, 2015); Light-Duty Vehicle Greenhouse Gas Emission Standards, 75 Fed. Reg. 25,324 (May 7, 2010).
[11] Id.
[12] Donald J. Trump (@realDonaldTrump), Twitter (Nov. 6, 2012, 2:15 PM), https://x.com/realdonaldtrump/status/265895292191248385?lang=en.
[13] See Stout, supra note 3.
[14] Id.
[15] Endangerment Finding, supra note 9.
[16] FCC v. Fox Television Stations, Inc., 556 U.S. 502, 515–16 (2009) (explaining policy reversal standard).
[17] Id.
[18] The panel, known as the Climate Working Group, was found by a federal court to have “met the statutory definition of an advisory committee under the Federal Advisory Committee Act (FACA)” and to have failed to comply with FACA’s procedural, open records, and fair-balance requirements; its violations were “established as a matter of law.” Judgment, Envtl. Def. Fund, Inc. & Union of Concerned Scientists v. Wright, No. 25-12249-WGY, at 1–3 (D. Mass. Jan. 30, 2026), https://storage.courtlistener. com/recap/gov.uscourts.mad.287748/gov.uscourts.mad.287748.99.0.pdf.
[19] See Carrie Jenks & Sara Dewey, The Legal Reasoning Behind the Endangerment Rescission, Salata Institute for Climate and Sustainability (Feb. 17, 2026), https://salatainstitute.harvard.edu/the-legal-reasoning-behind-the-endangerment-rescission/.
[20] 42 U.S.C. § 7521(a) (2018) (granting EPA authority to regulate emissions from new motor vehicles).
[21] The Supreme Courtdetermined in 2007 that greenhouse gases are “air pollutants” under the CAA and therefore subject to regulation. See Massachusetts, supra note 8.
[22] The Administrative Procedure Act § 706(2)(A) directs courts to set aside agency action that is “arbitrary, capricious, [or] an abuse of discretion.” See 5 U.S.C. § 706(2)(A).
[23] Procedural review under the APA necessarily incorporates a structured engagement with substantive evidence, especially in technically complex rulemakings. See, e.g., Motor Vehicle Mfrs. Ass’n v. State Farm Mut. Auto. Ins. Co., 463 U.S. 29 (1983) (requiring a reasoned explanation for agency rescission under arbitrary-and-capricious review); Encino Motorcars, LLC v. Navarro, 579 U.S. 211 (2016) (invalidating agency policy change for failure to provide a reasoned explanation and account for reliance interests).
[24] See Massachusetts, supra note 8.
[25] See Loper Bright Enters. v. Raimondo, 144 S. Ct. 2244 (2024).