For seventeen years, the Environmental Protection Agency's 2009 endangerment finding—the determination that carbon dioxide and five other greenhouse gases threaten public health—served as the legal foundation for virtually all federal climate regulation. On February 13, 2026, EPA Administrator Lee Zeldin officially revoked it, eliminating the basis for vehicle emissions standards, power plant rules, and regulations on oil and gas facilities in what the administration called 'the largest deregulatory action in American history.'
One week later, a wave of lawsuits hit federal courts as California, Massachusetts, Connecticut, and coalitions including Earthjustice, Environmental Defense Fund, Sierra Club, and public health groups like the American Lung Association challenged the revocation. These cases, filed primarily in the D.C. Circuit, argue the decision ignores settled science and violates the Clean Air Act, setting up a multi-year court battle likely headed to the Supreme Court that will determine federal authority over greenhouse gas emissions.
