What’s happening: The Trump administration is preparing to repeal the EPA’s 2009 “endangerment finding,” the legal determination that greenhouse gas emissions pose a threat to public health. That finding is the foundation for most federal climate rules, especially emissions standards for cars and trucks. If it goes away, the EPA would no longer have clear authority under the Clean Air Act to regulate those emissions.

This would mark a deeper shift than earlier rollbacks, moving beyond loosening regulations to undoing the legal basis behind them. Supporters frame it as a major deregulatory step aimed at lowering costs and expanding energy production, while critics note it would unwind a long-standing interpretation of the Clean Air Act that has shaped U.S. climate policy for more than a decade.