type: timeline_event
In March 2026, a coalition of health and environmental groups were pursuing legal challenges against the EPA's February 12, 2026 repeal of the 2009 Greenhouse Gas Endangerment Finding -- the legal foundation for all federal climate regulation under the Clean Air Act. The repeal, finalized under EPA Administrator Lee Zeldin and effective April 20, 2026, stripped the EPA of its authority to regulate carbon dioxide and other greenhouse gases, undoing the legal basis for vehicle emission standards, power plant regulations, and industrial pollution rules.
The EPA's justification for rescission rested on a contested legal interpretation that the Clean Air Act's section 202(a)(1) does not authorize the agency to prescribe emission standards in response to global climate change. Legal experts and the American Prospect characterized the legal reasoning as resting on shaky ground likely to face years of litigation that could ultimately reach the Supreme Court.
Among the specific rollbacks embedded in the repeal: all greenhouse gas emission standards for light-duty, medium-duty, and heavy-duty vehicles and engines for model years 2012 through 2027 and beyond were eliminated. These rules had been the cornerstone of U.S. climate policy for more than a decade.
The EPA's own internal scientific staff had confirmed the climate harms underpinning the original 2009 finding. Health and environmental groups noted that the EPA's rollback would result in an estimated 200,000 additional premature deaths over time according to modeling from the Environmental Protection Network. The repeal represented what the agency itself called the "largest deregulatory announcement in U.S. history" -- a characterization critics noted reflected a deliberate dismantlement of public health and environmental law in service of fossil fuel interests.