This removes the primary legal trigger used to set or tighten emissions standards for motor vehicles, power plants and other major sources, forcing any new federal climate rules to rely on alternative statutory authorities or new findings. Companies planning compliance investments tied to Clean Air Act GHG standards now face a near-term pause or redesign of federal requirements, shifting the burden to state-level programs and litigation outcomes. The change also creates a direct basis for regulated parties to challenge existing GHG rules that cite the endangerment finding as their predicate.