A coalition of 24 states, joined by additional cities and counties, filed a petition for review in the U.S. Court of Appeals for the District of Columbia Circuit challenging EPAâs rescission of the 2009 greenhouse-gas âendangerment finding.â ([nytimes.com](https://www.nytimes.com/2026/03/19/climate/epa-endangerment-states-lawsuit.html))
The 2009 endangerment finding concluded that greenhouse gases (including carbon dioxide) threaten public health and welfare, and it has functioned as a prerequisite for regulating GHG emissions from new motor vehicles under Clean Air Act Section 202. ([epa.gov](https://www.epa.gov/regulations-emissions-vehicles-and-engines/final-rule-rescission-greenhouse-gas-endangerment))
EPAâs February 2026 action also repealed greenhouse-gas emission standards for light-, medium-, and heavy-duty vehicles and engines, according to the Federal Register summary of the rule. ([federalregister.gov](https://www.federalregister.gov/documents/2026/02/18/2026-03157/rescission-of-the-greenhouse-gas-endangerment-finding-and-motor-vehicle-greenhouse-gas-emission))
The statesâ suit is expected to be consolidated or coordinated with a separate challenge brought earlier by public health and environmental groups (described by multiple outlets as the first major challenge to the repeal). ([abcnews.com](https://abcnews.com/Politics/wireStory/dozen-states-10-cities-sue-epa-repeal-endangerment-131230450))
The legal backdrop includes Massachusetts v. EPA (2007), where the Supreme Court held greenhouse gases can qualify as âair pollutantsâ under the Clean Air Act, enabling EPA regulation when statutory criteria are met. ([law.cornell.edu](https://www.law.cornell.edu/supct/html/05-1120.ZS.html))
Whatâs not resolved by the initial coverage: the administrationâs legal theory for rescinding the finding (e.g., statutory interpretation vs. evidentiary/scientific arguments) and how the court treats agency reversals under administrative law standards. ([federalregister.gov](https://www.federalregister.gov/documents/2026/02/18/2026-03157/rescission-of-the-greenhouse-gas-endangerment-finding-and-motor-vehicle-greenhouse-gas-emission))