On February 12, 2026, the U.S. Environmental Protection Agency finalized a rule rescinding the agency’s 2009 Greenhouse Gas Endangerment Finding — the formal legal determination that greenhouse gas emissions endanger public health and welfare. EPA Administrator Lee Zeldin called it ‘the single largest deregulatory action in U.S. history,’ citing claimed savings of over $1.3 trillion. The Endangerment Finding was not a regulation itself; it was the legal foundation that gave the EPA statutory authority to issue climate regulations under the Clean Air Act. By rescinding it, the EPA simultaneously repealed all federal greenhouse gas emission standards for motor vehicles, from passenger cars to heavy-duty trucks, and signaled that it no longer believes it has authority to regulate carbon emissions from power plants or other industrial sources either. Within hours of the rule’s publication in the Federal Register on February 18, environmental and public health organizations filed suit. Twenty-four states, ten cities, five counties, the District of Columbia, and the U.S. Virgin Islands followed with a separate lawsuit in March. The cases are now before the U.S. Court of Appeals for the D.C. Circuit, and legal analysts expect the dispute to eventually reach the Supreme Court.
What the Endangerment Finding Was
The Clean Air Act, first passed in 1963 and significantly amended in 1970 and 1990, requires the EPA to regulate air pollutants that ’cause, or contribute to, air pollution which may reasonably be anticipated to endanger public health or welfare.’ The law does not list specific pollutants by name for most of its provisions; instead it requires the EPA to make findings — based on science — about whether a given substance meets that threshold. In 2003, the Bush administration’s EPA said it did not believe it had authority under the Clean Air Act to regulate greenhouse gases as air pollutants. A coalition of states led by Massachusetts sued. On April 2, 2007, the Supreme Court ruled 5-4 in Massachusetts v. EPA that greenhouse gases are in fact air pollutants covered by the Clean Air Act, and that the EPA was legally required to determine whether they endanger public health and welfare or to provide a scientific justification for declining to do so. In December 2009, under President Obama and EPA Administrator Lisa Jackson, the agency issued its formal Endangerment Finding: it determined that six greenhouse gases — carbon dioxide, methane, nitrous oxide, hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride — endanger the public health and welfare of current and future generations. That determination triggered the EPA’s legal obligation to regulate those emissions under the Clean Air Act. It also became the legal foundation on which every subsequent major federal climate regulation was built.
What the Rescission Does
The February 2026 final rule does two things simultaneously. First, it rescinds the 2009 Endangerment Finding itself, declaring that EPA no longer believes Clean Air Act Section 202(a) authorizes the agency to regulate greenhouse gas emissions from motor vehicles on the basis of global climate change concerns. Second, it repeals all federal greenhouse gas emission standards that were issued under the authority of that finding: standards for light-duty vehicles such as passenger cars and SUVs, medium-duty vehicles, and heavy-duty trucks and engines, along with associated test procedures, reporting requirements, and related regulations. The practical effect on vehicles is immediate: the federal standards that required automakers to meet progressively stricter fuel economy and emissions targets no longer exist at the federal level. Beyond vehicles, the rescission’s rationale extends to stationary sources — power plants, factories, oil and gas operations. The EPA had separately issued greenhouse gas emission standards for new fossil fuel-fired power plants under Section 111 of the Clean Air Act. EPA proposed in June 2025 to repeal those standards as well, arguing that the same statutory logic that applies to vehicles applies to power plants: the agency concluded that fossil fuel-fired plants do not ‘contribute significantly to dangerous air pollution’ within the meaning of the statute, despite power plants being the largest stationary source of greenhouse gas pollution in the United States. That power plant proposal has not yet been finalized as of this writing.
The Agency’s Legal Argument
The EPA’s rescission does not rest on a scientific argument. The agency did not claim that climate change is not occurring or that greenhouse gas emissions do not affect the climate. The National Academies of Sciences reaffirmed the underlying climate science as recently as late 2025. Instead, the EPA’s argument is statutory: it contends that Clean Air Act Section 202(a) was not intended by Congress to address global climate change, and that the 2007 Supreme Court ruling in Massachusetts v. EPA does not actually compel a finding of endangerment — only that EPA must make a considered determination. EPA argues that upon reconsidering that determination, it concludes the statute does not reach the problem of global climate change as a public health matter under the Clean Air Act’s existing framework. Critics, including the 24 state coalition and multiple law school clinics and environmental organizations, argue this interpretation directly contradicts what the Supreme Court already decided in 2007. They contend the Court’s ruling established that greenhouse gases are air pollutants subject to the Clean Air Act and that the agency cannot simply reinterpret the statute to say otherwise without Congress changing the law. They also point to the fact that the National Academies affirmed the science, meaning EPA’s basis for reversal is entirely legal rather than empirical.
Who Sued and What They Are Arguing
Two parallel waves of litigation followed the rule’s publication. Within hours of February 18, seventeen environmental and public health organizations — including the Clean Air Task Force, the Natural Resources Defense Council, and the Sierra Club — filed a petition for review in the U.S. Court of Appeals for the D.C. Circuit. On March 19, a second petition was filed by a coalition led by the attorneys general of New York, Massachusetts, California, and Connecticut. That coalition ultimately included 24 states, 10 cities, 5 counties, the District of Columbia, the U.S. Virgin Islands, and the Pennsylvania Department of Environmental Protection — Case No. 26-1061 in the D.C. Circuit. The challengers make several overlapping arguments. They contend the rescission is unlawful because it contradicts the Supreme Court’s 2007 ruling in Massachusetts v. EPA, which they argue requires the EPA to regulate greenhouse gases once they are determined to endanger public health. They argue EPA cannot simply reinterpret the Court’s statutory analysis away. They also argue the rescission is arbitrary and capricious — meaning the agency failed to provide a reasoned explanation for reversing a decision that has been in place for 17 years and that the underlying scientific record has not changed. The D.C. Circuit is the standard venue for challenges to major EPA rules and has ruled against major Trump administration deregulatory actions in prior terms.
What Happens If the Courts Uphold It
If the D.C. Circuit upholds the rescission and the Supreme Court ultimately affirms it, the United States would have no federal statutory authority to regulate greenhouse gas emissions from motor vehicles or power plants under the Clean Air Act. States that have their own greenhouse gas regulations — California, New York, Massachusetts, and others — could still enforce their own standards. But federal vehicle standards would remain repealed, and automakers would face a patchwork of varying state requirements rather than a national floor. International automakers would still need to comply with emissions standards in Europe, Japan, and other markets where such rules remain in effect. For power plants, a final repeal of Section 111 standards would mean no federal cap on greenhouse gas output from coal and gas-fired electricity generation. The Bulletin of the Atomic Scientists described the rescission as eliminating ‘the legal basis for nearly every major U.S. climate regulation.’ If the courts strike the rescission down, the 2009 Endangerment Finding would be restored and the EPA would be legally obligated to regulate greenhouse gases — though the current administration would likely pursue new administrative or legislative avenues to avoid doing so.
Where Things Stand
As of late July 2026, the litigation is advancing in the D.C. Circuit. Briefing schedules have been set and both sides have filed preliminary materials. Legal analysts across the political spectrum expect the case to reach the Supreme Court, where the current six-justice conservative majority would have the final word on the scope of EPA’s authority under the Clean Air Act. The outcome would have direct implications not only for U.S. climate policy but for the broader question of how much authority federal agencies retain to regulate areas of public health where Congress has not passed specific, targeted legislation. The Supreme Court’s 2022 ruling in West Virginia v. EPA had already significantly curtailed the agency’s power to reshape electricity markets through Section 111, but had not addressed the Endangerment Finding directly. The current litigation will test whether the administration’s interpretation of that statutory limit — taken to its logical conclusion — can survive judicial review.