Challenges to EPA's Repeal of the 2009 Endangerment Finding
Introduction
On February 12, 2026, the U.S. Environmental Protection Agency ("EPA") finalized a rule repealing the 2009 Endangerment Finding—the agency's formal determination that greenhouse gas ("GHG") emissions from motor vehicles contribute to air pollution that endangers public health and welfare—and repealing all federal GHG emission standards for motor vehicles and engines. Two waves of litigation have followed shortly after the publication of the final rule, and continue to develop as briefing is scheduled.
Background: The Endangerment Finding and Its Rescission
The 2009 Endangerment Finding was the direct result of the landmark 2007 Supreme Court decision in Massachusetts v. EPA, in which the Court held that greenhouse gases are "air pollutants" under the Clean Air Act and directed EPA to determine, based on the science, whether such emissions endanger public health or welfare. Following years of scientific review, EPA concluded in 2009 that six key GHGs—including carbon dioxide and methane—threaten the health and welfare of current and future generations. That finding served as the legal foundation for vehicle emission standards across three successive presidential administrations.
In the final rule, EPA advanced a primarily legal rationale for rescission, arguing that the Clean Air Act does not provide statutory authority to prescribe motor vehicle emission standards "for the purpose of addressing global climate change concerns." The agency relied in part on more recent Supreme Court decisions, including the 2022 West Virginia v. EPA ruling, invoking the major questions doctrine, and the 2024 Loper Bright decision, overruling Chevron deference.
The Challenges: Two Tracks of Litigation
The legal challenges are proceeding on two tracks in the U.S. Court of Appeals for the D.C. Circuit. One is being led by a coalition of health and environmental organizations while the other is being led by a coalition of state and local governments. Both challenge EPA's final rule, and should be monitored closely as they continue to develop.
Health and environmental organizations challenge: The first lawsuit, filed on February 18, 2026 (Case No. 26-01037), was brought by a broad coalition of 17 health and environmental organizations, including: American Public Health Association, American Lung Association, Natural Resources Defense Council, Sierra Club, Environmental Defense Fund, Center for Biological Diversity, and others. The lawsuit named EPA Administrator Lee Zeldin and EPA as defendants.
On April 16, 2026, 16 health and environmental groups—many of whom are also plaintiffs in the D.C. Circuit litigation—filed a separate administrative petition with EPA, asking the agency to reconsider its rescission. Docket No. EPA-HQ-OAR-2025-0194. The petition argues that the rescission was "incorrect and [made] unsupported claims that reducing climate pollution from U.S. cars and trucks is 'futile.'" The petition seeks EPA reconsideration of the repeal.
Following this separate administrative petition with EPA, parties lodged a motion to delay the merits briefing in the D.C. Circuit case until June 2026, pending EPA action on the reconsideration petitions. If granted, this may delay merits briefing until the administrative petition has been resolved.
State and local government challenge: One month after the initial lawsuit was filed, an additional lawsuit was filed on March 19, 2026 (Case No. 26-1061) by a coalition led by the attorneys general of New York, Massachusetts, California, and Connecticut. This petition for review challenging the rescission was joined by a total of 24 states, 10 cities, five counties, the District of Columbia, the U.S. Virgin Islands, and the Pennsylvania Department of Environmental Protection. Similar to the first case, there is currently a motion pending to delay the merits briefing until June 2026, pending EPA action on the reconsideration petition. In total, roughly 40 states, counties, and cities are parties to the state-led petition.
Outlook
The issues flowing from EPA's decision to rescind the 2009 Endangerment Finding continue to develop. While the lawsuits may be delayed due to the administrative reconsideration sought, the progress of these lawsuits—and any other challenges—should be monitored as they continue to evolve.
