In February 2026, Sierra Club sued the Trump Administration over its largest attack on climate protection: its withdrawal of EPAs longstanding determination that greenhouse gas pollution endangers public health and welfare, otherwise known as the endangerment finding. This determination, made in 2009, has provided the foundation for EPA’s climate pollution standards for vehicles, power plants, oil and gas infrastructure, and other key sources of greenhouse gas emissions ever since.
In Massachusetts v. EPA, the Supreme Court held that greenhouse gases are climate pollutants under the Clean Air Act and must be regulated if EPA finds that they endanger health and welfare. Now, Trump’s EPA is attempting to sidestep Massachusetts v. EPA by reviving the very reasoning that the Court rejected in that case.
The heart of EPA’s justification is that US regulations will do nothing to stop climate change, and so the Clean Air Act could not possibly countenance such an exercise in futility. This rationale is profoundly wrong, and Sierra Club will fight vigorously in court to oppose these claims, defend the endangerment finding, and ensure that Massachusetts v. EPA continues to be the law. While EPA’s withdrawal of the endangerment finding applies specifically to greenhouse gas standards for vehicles—which it has eliminated across-the-board—the agency will soon follow suit for other sectors such as power plants, and Sierra Club will litigate those actions too.
Sierra Club has been involved in litigation to secure federal climate standards under the Clean Air Act for longer than any other organization. In 2002, Sierra Club sued EPA over its failure to respond to a rulemaking petition demanding greenhouse gas standards for vehicles, which it had ignored for years. That litigation set in motion the chain of events that led to the landmark Massachusetts decision, the endangerment finding, and the Clean Air Act standards we now seek to defend. Over 20 years after that initial case, we are going back to court to defend the strongest tool that EPA has to protect against climate change.
Sierra Club is represented in this case by Senior Attorney Andres Restrepo.