EPA rescinds greenhouse gas Endangerment Finding and eliminates mobile source GHG emissions standards

On February 18, 2026, the United States Environmental Protection Agency (EPA) published a historic final rule rescinding the Agency’s 2009 determination that greenhouse gas (GHG) emissions from motor vehicles and engines contribute to air pollution that endangers public health and welfare (Endangerment Finding). See 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). The final rule also repeals all GHG emission standards for new light-, medium-, and heavy-duty motor vehicles and engines manufactured for sale in the US, both prospectively and for all prior model years.

Beyond the repeal of all GHG emission standards for motor vehicles and engines, rescission of the Endangerment Finding also eliminates much of the foundation for other federal GHG emissions standards and climate change mitigation regulations and policies implemented over the past 15 years. As a result, the final rule may have additional far-reaching ramifications for industries outside of the transportation sector, including those involving stationary air emissions sources such as power plants and various manufacturing and industrial facilities.

The first court challenges to the rule were filed in federal court by environmental and public health organizations and advocates, the day the rule was published.

Reshaping US transportation and climate policy

An EPA fact sheet regarding the final rule characterizes the Endangerment Finding rescission as “the single largest deregulatory action in U.S. history,” which “delivers $1.3 trillion in relief [to American consumers] from crushing regulations.” EPA Administrator Lee Zeldin’s statement summarized the action as follows:

Referred to by some as the ‘Holy Grail’ of the ‘climate change religion,’ the Endangerment Finding is now eliminated. The Trump EPA is strictly following the letter of the law, returning commonsense to policy, delivering consumer choice to Americans and advancing the American Dream. As EPA Administrator, I am proud to deliver the single largest deregulatory action in U.S. history on behalf of American taxpayers and consumers.

EPA’s new rule is the final step implementing a directive in a January 2025 Executive Order entitled “Unleashing American Energy,” which ordered EPA to evaluate the “legality and continuing applicability” of the Endangerment Finding. In March 2025, EPA recommended reconsideration of the Finding and all regulations and actions predicated on it. Then, in August 2025, the Agency issued a proposed rule that would repeal the Endangerment Finding. The final rule published February 18, 2026, follows public notice, comment, and EPA review.

The final rule is scheduled to take effect on April 26, 2026. Petitions for review challenging the rule have already been filed in the DC Circuit, and ultimately the validity of the rule may be determined by the US Supreme Court.

Background and overview of the Endangerment Finding

Section 202(a)(1) of the Clean Air Act (CAA) requires EPA to prescribe by regulation “standards applicable to the emission of any air pollutant from any class or classes of new motor vehicles or new motor vehicle engines, which in [EPA’s] judgment cause, or contribute to, air pollution which may reasonably be anticipated to endanger public health or welfare.”

In 2007, the US Supreme Court’s landmark 5–4 decision in Massachusetts v. EPA rejected the Agency’s finding that it lacked authority to regulate GHG emissions under the Clean Air Act. Finding that CAA Section 202(a)’s broad definition of “air pollutant” encompassed GHGs, the Court held that the Act granted EPA the statutory authority to regulate GHG emissions from new motor vehicles and engines if those emissions endanger public health or welfare. The Court left EPA to determine whether GHG emissions from motor vehicles “cause or contribute to” pollution “anticipated to endanger public health or welfare.”

Two years after Massachusetts, EPA issued the Endangerment Finding, concluding that six “well-mixed” GHGs – carbon dioxide (CO₂), methane (CH₄), nitrous oxide (N₂O), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF₆) – contribute to air pollution in amounts projected to threaten public health and welfare. Four of those GHGs are emitted by motor vehicles and combustion engines.

Based on the Endangerment Finding, EPA has issued a series of annual GHG emissions standards for motor vehicles and engines manufactured for sale in the US, starting with model year 2012.

Final rule rescinding the Endangerment Finding and vehicle GHG emissions standards

EPA’s final rule primarily relies on legal rationales for its rescission of the Endangerment Finding and repeal of federal GHG emission standards for motor vehicles. Simplified, the final rule’s primary conclusions are that EPA lacks statutory authority to regulate such emissions and, therefore, evidence regarding whether and to what extent GHG emissions may contribute to climate change is legally irrelevant.

The proposed rule had posited “superseding” scientific and evidentiary findings as an alternative basis for the repeal, but the final rule expressly declines to make such findings, determining that, “[b]ecause we conclude that CAA section 202(a)(1) does not authorize the EPA to regulate in response to global climate change concerns, this final action does not turn on scientific findings made with respect to the validity, certainty, or extent of global climate change.” Following is a summary of the primary legal bases for final rule’s rescission of the Endangerment Finding.

Legal bases for rescission of the Endangerment Finding

• Best reading of “air pollution”: EPA concludes that the term “air pollution” under CAA Section 202(a)(1) is “best read in context as pollution that threatens health or welfare through local or regional exposure.” In contrast, GHG emissions are mixed in the atmosphere, and even local climate change impacts are attributable to global GHG concentrations.


• No standalone endangerment finding: EPA determines that it lacks procedural discretion under the CAA to (i) “issue standalone endangerment findings that trigger a duty to regulate without analyzing and promulgating the required emission standards,” or (ii) “prescribe standards without making the requisite findings for the air pollutant emissions and . . . motor vehicles or engines at issue.”


• Regulated emissions must cause or contribute to endangerment: EPA finds that the Endangerment Finding erroneously “severed” that finding from causation or contribution, and thus failed to establish a specific nexus between the particular emissions at issue (i.e., vehicle GHG emissions in the US) and the identified dangers to public health or welfare (US effects of global climate change). The Agency concludes that emissions regulation under CAA Section 202(a)(1) requires a finding that the US emissions themselves endanger public health or welfare, not as part of a mixture with international emissions that are outside the scope of the Act.


• Recent Supreme Court separation of powers decisions. EPA finds further legal support for its recission of the Endangerment Finding in recent Supreme Court decisions, including:


• Loper Bright Enterprises v. Raimondo, which requires agencies to apply the best interpretation – not merely a reasonable interpretation – of statutes, including those that are silent or ambiguous on questions of law. EPA concludes that the best reading of CAA 202(a)(1) is that it does not authorize regulation of GHG emissions merely because it finds those emissions contribute to global climate change. This conclusion is arguably in tension with the Supreme Court’s finding in Massachusetts v. EPA.


• West Virginia v. EPA. Relying on the major questions doctrine adopted in West Virginia, the final rule concludes that “the appropriate policy response to global climate change concerns is a decision vested in Congress, and Congress did not decide the Nation’s policy response to these concerns when it enacted CAA Section 202(a)(1) to address domestic air pollution problems nearly sixty years ago, or in any subsequent amendment thereto.”

Separate futility rationale for repealing the GHG emission standards

• EPA finds the GHG emission standards have no meaningful effect on global climate change: Separate from EPA’s rescission of the Endangerment Finding, the Agency finalized a separate, independent basis for repealing the GHG emission standards for motor vehicles. The Rule states that climate impact modeling submitted by commenters and Agency analysis indicate that even the elimination of all GHG emissions from new and existing vehicles in the US would have a de minimis impact on global mean surface temperature (GMST) and global mean sea level rise (GSLR), two common measures of climate change.
  
  EPA estimates the effect of such complete elimination of US vehicle GHG emissions on GMST and GSLR by the year 2100 would be less than the accepted variability of those measurements. The Agency also estimates that compliance with US motor vehicle GHG emission standards would impose costs exceeding $1 trillion. The Agency concludes it would be unreasonable to maintain such costly regulations without either (i) materially improving public health or welfare, or (ii) an explicit statutory mandate to do so.

EPA Rule could set the stage for overruling Massachusetts v. EPA

The 2009 Endangerment Finding was an outgrowth from the Supreme Court’s 5–4 decision in Massachusetts v. EPA holding that GHGs are “air pollutants” within the broad definition set forth in the CAA. While there are some differences between the Court’s ruling on the merits in that case and EPA’s current reasoning in rescinding the Endangerment Finding, there is considerable tension between EPA’s core conclusion (Agency lacks statutory authority to regulate) and the primary substantive holding of Massachusetts (Agency has such statutory authority). It thus appears that challenges to the final rule ultimately may be decided by the Supreme Court.

No member of the five-justice majority in Massachusetts remains on the Court today. At the same time, three of the four dissenters continue to serve on the Court. West Virginia, Loper Bright, and other recent Supreme Court decisions represent a shift away from Executive agency power to broadly interpret laws and fill gaps in statutes in the absence of clear and specific congressional direction. And at least two of the six justices appointed to the Court since Massachusetts may be receptive to an argument that the case was incorrectly decided. Thus, if a challenge to rescission of the Endangerment Finding is resolved by the Supreme Court, it is possible that the Court would both uphold the EPA rule and overrule Massachusetts v. EPA, in whole or in part.

EPA’s new rule raises a number of significant legal and policy questions that are beyond the scope of this initial summary. DLA Piper teams will explore some of those issues, and their implications for businesses and others, in upcoming client alerts.

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DLA Piper’s Transportation and Environment, Health and Safety attorneys assist and advise clients on regulatory and policy developments affecting the motor vehicle industry as well as stationary sources of air emissions. If you have questions regarding these developments, please contact one of the authors or your regular DLA Piper contact.