California and Connecticut are preparing a coordinated legal challenge after the EPA rescinded the endangerment finding, the 2009 determination that enables federal greenhouse gas regulation under the Clean Air Act.
California and Connecticut are preparing a coordinated legal challenge to the U.S. Environmental Protection Agency’s repeal of the endangerment finding, the legal basis for federal climate regulation, attorneys general from both states said Wednesday. As reported exclusively by Reuters, the move marks a significant escalation in state opposition to federal climate rollback efforts.
The states are responding to the EPA’s decision last week to rescind the endangerment finding, the 2009 determination that greenhouse gases pose a threat to public health and welfare. That finding has underpinned a range of federal climate rules, including vehicle emissions standards and power plant regulations.
Connecticut Attorney General William Tong said his office is evaluating whether it has standing and what legal claims to bring, adding that the priority is to “make sure we have a tight case.” Tong said he has spoken with his California counterpart about cooperation, but has not set a timeline for filing a lawsuit.
California Attorney General Rob Bonta said states are looking at the legal reasons for challenging the EPA’s action. “We are examining the impact of the repeal on federal authority to regulate greenhouse gases,” he said in an interview. Bonta declined to comment on specific legal theories but said any challenge will be grounded in administrative law and statutory interpretation.
The repeal of the endangerment finding removes the scientific and legal justification for regulating greenhouse gases under the Clean Air Act. The EPA did not immediately respond to a request for comment on the states’ plans.
Environmental groups and Democratic lawmakers have strongly criticized the EPA’s decision, saying it undermines science-based regulation and public health protections. Trump administration officials defended the repeal as a means to reduce regulatory burdens on industry.
Legal experts say the states may seek to argue that the EPA’s reversal of the endangerment finding is arbitrary and capricious, a standard under the Administrative Procedure Act that courts apply when reviewing agency actions. They may also argue that the Clean Air Act continues to require the agency to regulate pollutants that endanger health.
The endangerment finding originated in 2009, following the Supreme Court’s decision in Massachusetts v. EPA, which held that greenhouse gases qualified as air pollutants under the Clean Air Act. Based on that finding, the EPA adopted standards for vehicle emissions and other greenhouse gas sources. These rules together have targeted a significant portion of national emissions.
Opponents of the repeal view it as a direct attack on the legal authority for federal climate policy. Without the endangerment finding, rules that rely on it could face fresh legal challenges. Supporters of the repeal argue that the finding imposed burdensome regulations and that Congress, not the EPA, should determine climate policy.
The coordinated effort by California and Connecticut signals that states are preparing to counter the federal rollback through the courts. How quickly they move and whether additional states join the effort will shape the next phase of litigation.
Legal observers say a successful challenge could reinstate the finding or compel the agency to provide a stronger scientific basis for its decision. A loss for the states could leave the EPA with greater discretion to limit greenhouse gas regulation under current law. The broader implications extend beyond a single rule. The endangerment finding has served as the legal backbone for climate regulation in the United States for more than a decade. Its removal represents one of the most significant shifts in federal environmental policy in recent years and follows a broader trend of regulatory reversals on climate and energy issues.
