As a major shift in federal climate policy moves into the courtroom, the federal government is fighting to give up its legal authority to regulate greenhouse gases.
In February 2026, the Environmental Protection Agency rescinded its 2009 endangerment finding, or the determination that greenhouse gases threaten public health and welfare and can therefore be regulated under the 1970 Clean Air Act.
The EPA now holds that Section 202(a) of the Clean Air Act does not authorize the agency to regulate vehicle emissions. In responses, multiple lawsuits have been filed directly in the U.S. Court of Appeals for the District of Columbia Circuit, with a case expected to go before the U.S. Supreme Court.
For legal observers, the suits raise a fundamental question: Can a federal agency reverse a finding that has anchored regulation for more than a decade?
Chris Winter, executive director of the Getches-Wilkinson Center for Natural Resources,
Energy and the Environment at the University of Colorado Law School, said the dispute turns on how courts interpret the Clean Air Act and Supreme Court precedent.
“The primary argument that EPA is making is that Congress only intended for EPA to have authority over air pollution that would affect human health or welfare as a result of local or regional exposures,” Winter said. “EPA tries to draw this distinction between local and regional pollution versus global pollution.”
But, he added, “there’s nothing in the statute itself — there’s no textual basis — for that distinction.”
Under the Clean Air Act, EPA can regulate pollutants that “may reasonably be anticipated to endanger public health or welfare.” Winter explained, “The statute says, ‘any air pollution.’ Congress defined that term very broadly.”
A broad interpretation was central to the Supreme Court’s 2007 decision in Massachusetts v. EPA, which held that greenhouse gases qualify as air pollutants and confirmed EPA’s authority to regulate them.
“I think EPA’s position conflicts with the text of the statute and conflicts with binding Supreme Court precedent,” Winter said. “Many people who have worked in this area for a long time see this as a tremendous mistake in terms of legal reasoning.”
While reversing course on a policy is permitted under administrative law, agencies must provide a reasoned explanation.
Winter said that requirement could become a focal issue, especially given the central role the endangerment finding has played in previous federal climate regulation.
In support of its new approach, EPA has pointed to recent Supreme Court rulings, including decisions that limit government power.
Nonetheless, Winter suspects a rereading of the Climate Air Act may not resonate. “What’s interesting here is that EPA says it’s really basing this on context rather than the actual text,” he said. “It’ll be interesting to see whether the Court remains faithful to its textualist approach to interpretation and stare decisis or whether it’s willing to go off in a different direction in this situation.”
The EPA rescinding also touches on another recurring legal issue in environmental regulation: whether individual regulatory actions must directly solve a global problem.
“There is nothing in the Clean Air Act itself that says each regulatory action has to be the silver bullet that solves the problem,” Winter said. “Oftentimes, air quality impacts result from many different sources. That’s the nature of the way the world works in this area.”
Addressing a similar question in Massachusetts v. EPA, the Supreme Court concluded that incremental reductions fall within the agency’s authority.
If the Court sides with EPA this time, far more than the dysregulation of vehicle emissions could be in play.
“I think EPA certainly understands that the endangerment finding not only served as a basis for controlling greenhouse gas emissions from mobile sources but also from power plants and oil and gas production facilities,” Winter said. “People are quite concerned that we’re going to see this initial rollback bleed over into other sectors.”
For Colorado, the stakes are significant. “The federal government has primacy in regulating tailpipe emissions,” he said. “States like Colorado can do a lot — provide incentives for electric vehicles, build out charging infrastructure, invest in public transit — but they can’t step in and directly regulate those emissions the way EPA can.”
Should the Supreme Court conclude that EPA does not have authority to regulate greenhouse gas emissions, “that would be a very difficult place for us to be,” Winter said. “At that point, the conversation would inevitably shift back to Congress.”