type: timeline_event
In late February and continuing into early March 2026, a coalition of environmental and public health groups pressed legal challenges against the Trump EPA's repeal of the landmark "endangerment finding" — the 2009 scientific determination that greenhouse gases constitute a threat to public health and welfare. The endangerment finding was the foundational legal basis for nearly all federal climate regulation, and its repeal represented the most sweeping environmental deregulatory act since the modern regulatory state was established.
Earthjustice, the Clean Air Task Force, and a coalition of 17 health and environmental organizations filed a petition in the U.S. Court of Appeals for the D.C. Circuit challenging the EPA's final rule repealing the endangerment finding and simultaneously eliminating vehicle emission standards that had been established under it. Separately, a group of 18 youth climate activists filed their own petition. Additional lawsuits were expected.
Environmental lawyers argued the repeal was legally untenable because it contradicted Supreme Court precedent from Massachusetts v. EPA (2007), which the Trump EPA was attempting to relitigate without a changed factual record. EPA Administrator Lee Zeldin had announced the repeal as part of a broader agenda to roll back 31 regulatory actions, framing it as necessary for energy independence and economic competitiveness.
Legal analysts writing in The American Prospect assessed the repeal's prospects in court as poor, noting that the EPA had not offered new scientific evidence contradicting the underlying findings but had instead attempted to reweigh established science using ideological and economic rationales that courts had previously rejected. The cases were expected to ultimately reach the U.S. Supreme Court, where the administration hoped its conservative supermajority would sustain the rollback.