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A coalition of health and environmental groups sued the Environmental Protection Agency on Wednesday, challenging the agency’s move to rescind a 2009 finding that greenhouse gas emissions threaten public health and welfare. The groups said the repeal eliminates the core legal basis for Clean Air Act climate rules and could unwind greenhouse gas standards across multiple categories of pollution sources. The lawsuit was filed in the U.S. Court of Appeals for the District of Columbia Circuit.
The EPA last week finalized a rule that revoked the 2009 “endangerment finding,” a determination made during the Obama administration. The finding concluded that carbon dioxide and other greenhouse gases pose risks to public health and welfare, and the EPA has used that framework for major greenhouse gas regulations since the 2007 Supreme Court decision known as Massachusetts v. EPA. In that earlier ruling, the Supreme Court held that carbon dioxide and other greenhouse gases are “air pollutants” under the Clean Air Act.
The groups’ legal filing argues that EPA’s rescission is unlawful. The lawsuit asserts that the agency’s decision to reverse the 2009 finding conflicts with the science and legal analysis that supported the original determination and with the courts’ longstanding rejection of challenges to the endangerment finding. The coalition said the change also undermines vehicle emissions standards that were part of a broader climate regulatory structure under the Clean Air Act.
The lawsuit seeks to block the repeal’s effects, which attorneys and other experts said could go beyond cars and trucks. The EPA rule rescinded the endangerment finding and removed safeguards tied to it, and experts said that could enable a broader undoing of climate regulations for stationary sources such as power plants and oil and gas facilities. The groups said the underlying evidence supporting the endangerment finding has only grown stronger since it was approved.
Brian Lynk, a senior attorney with the Environmental Law & Policy Center, said the agency cannot credibly claim that the scientific body of work supporting the 2009 endangerment finding is now incorrect. Lynk also described the EPA’s decision as creating immediate uncertainty for businesses, guaranteeing prolonged legal battles, and undermining stability for federal climate regulations.
EPA spokeswoman Brigit Hirsch said Wednesday that the agency “carefully considered and reevaluated the legal foundation of the 2009 Endangerment Finding” in light of recent court decisions. She pointed to the legal limits that the Supreme Court set in 2022 on how the Clean Air Act can be used to reduce carbon dioxide emissions from power plants and said the EPA is bound by laws established by Congress. Hirsch also said Congress “never intended” for EPA to have authority to impose greenhouse gas regulations for cars and trucks.
The dispute is likely to return to the Supreme Court, where, as the complaint and reporting noted, the court is now far more conservative than it was in 2007. The Supreme Court’s Massachusetts v. EPA decision has been central to the endangerment finding’s durability, and courts have repeatedly rejected legal challenges to it, including a 2023 decision by the D.C. appeals court.
The lawsuit names the EPA and its administrator, Lee Zeldin, as defendants. The coalition includes groups such as the American Public Health Association, American Lung Association, Alliance of Nurses for a Healthy Environment and Physicians for Social Responsibility, along with environmental groups including the Center for Biological Diversity, Conservation Law Foundation, Environmental Defense Fund, Natural Resources Defense Council and Sierra Club.
The filing reflects the competing narratives around the repeal. President Donald Trump described the rescission as “the single largest deregulatory action in American history, by far,” while Zeldin called the endangerment finding “the Holy Grail of federal regulatory overreach.” Zeldin said the endangerment finding “led to trillions of dollars in regulations that strangled entire sectors of the United States economy,” and the groups suing the EPA described the move as the biggest attack on federal authority to address climate change.
Separate from the court challenge, Senate Democrats announced they are launching an investigation into the EPA’s decision. They said public comments by Zeldin and other Trump officials over the past year indicated the administration regarded repeal of the endangerment finding as a predetermined objective before it completed required regulatory review, including consideration of nearly 600,000 public comments. Rhode Island Sen. Sheldon Whitehouse, the top Democrat on the Senate Environment Committee, is leading the inquiry with 40 other senators.
“When an agency signals that the outcome of a proceeding is preordained, public participation becomes performative rather than meaningful, undermining the legitimacy of the rulemaking process and violating basic principles of administrative law,” Whitehouse and other Democrats said in a letter to Zeldin.
The case is expected to test how the EPA interprets its Clean Air Act authority after court rulings that have narrowed aspects of greenhouse gas regulation. While the administration said the repeal would reduce costs and regulatory burdens, the groups challenging the EPA said the endangerment finding remains a lawful and necessary legal foundation for safeguards tied to greenhouse gas emissions.