The Trump administration will formally rescind the 2009 endangerment finding on Thursday, eliminating the legal foundation the federal government has used for more than 16 years to regulate greenhouse gas emissions under the Clean Air Act. White House press secretary Karoline Leavitt announced the move during a briefing on Tuesday, calling it "the largest deregulatory action in American history" and estimating it would save Americans $1.3 trillion in regulatory costs.

President Trump will be joined at the ceremony by EPA Administrator Lee Zeldin, who has described the endangerment finding as "the holy grail of climate change religion" and called it "one of the most damaging decisions in modern history."

The finding, issued under President Obama, concluded that six greenhouse gases — including carbon dioxide and methane — "threaten the public health and welfare of current and future generations." That determination gave the EPA administrator authority to regulate emissions from motor vehicles under Section 202(a) of the Clean Air Act. It subsequently served as the regulatory underpinning for emissions standards across vehicles, power plants, and oil and gas operations through both the Obama and Biden administrations.

Its repeal goes well beyond what Trump pursued during his first term. From 2017 to 2021, the administration loosened auto emissions standards but left both the standards themselves and the endangerment finding intact. This time, the EPA is moving to eliminate the legal basis for those standards entirely.

What the repeal covers

The final rule will directly eliminate all federal greenhouse gas emission standards for light-, medium-, and heavy-duty vehicles and engines. The EPA said that without the endangerment finding, the agency "would lack statutory authority under Section 202(a) of the Clean Air Act to prescribe standards for certain motor vehicle emissions."

Zeldin told the Wall Street Journal that the final rule applies specifically to vehicle emissions, not to stationary sources such as power plants or oil and gas facilities. However, the agency has separately proposed to find that emissions from power plants "do not contribute significantly to dangerous air pollution" and therefore should not be regulated — a parallel effort that could accomplish a similar goal for the power sector through a different legal mechanism.

The repeal would erase Biden-era tailpipe emissions rules finalized in 2024 that aimed to cut passenger vehicle fleetwide emissions by nearly 50 percent by 2032 compared with 2027 projected levels. The EPA had forecast that between 35 and 56 percent of new vehicles sold between 2030 and 2032 would need to be electric under those rules, and projected net benefits of $99 billion annually through 2055 — including $46 billion in reduced fuel costs and $16 billion in reduced maintenance and repair costs.

The Trump administration projects the repeal will save consumers an average of $2,400 per vehicle on new purchases. Leavitt framed the action as part of a broader affordability agenda. "This is just one more way this administration is working to make life more affordable for everyday Americans," she said.

The White House also announced that on Wednesday, Zeldin and Energy Secretary Chris Wright will hold a separate event to "tout clean, beautiful coal" and announce an executive order directing the Department of Defense to purchase electricity from coal-fired power plants. The administration plans to award funding to five coal plants in West Virginia, Ohio, North Carolina, and Kentucky for recommissioning and upgrades.

The legal and scientific backdrop

The endangerment finding traces its origins to a 2007 Supreme Court decision in Massachusetts v. EPA, which held that greenhouse gases qualify as air pollutants under the Clean Air Act and should be regulated if found to threaten public health. The Obama EPA issued the finding two years later, concluding that rising ambient ozone, increased heat wave mortality, and the intensification of extreme weather events all supported the determination.

Since then, courts have uniformly rejected legal challenges to the finding, including a 2023 decision by the U.S. Court of Appeals for the D.C. Circuit. The National Academies of Sciences, Engineering and Medicine conducted a review in response to the EPA's proposed repeal and declared the reality and threat of climate change "beyond scientific dispute."

The EPA is expected to lean on novel statutory arguments rather than directly challenging the underlying science. The agency is likely to argue that the Clean Air Act's vehicle emissions provisions were designed to address pollution that harms people through local or regional exposure — and that greenhouse gas emissions impact public health only "indirectly" through global climate change, making regulation an unlawful exercise of EPA authority.

Benjamin DeAngelo, a former EPA official who helped write the 2009 finding, said that reading of the statute is wrong. He pointed to the Clean Air Act's successful use in the 1980s to restrict ozone-depleting chemicals — another class of pollutants whose harm was global rather than local. "Nowhere does it say in that act that the endangerment caused by the pollution must be local in nature," DeAngelo said.

A Department of Energy report written to support the repeal's scientific arguments ran into legal trouble after a federal court in Massachusetts ruled in January that the advisory group that produced it was formed in violation of federal law.

Industry reaction is split

The auto industry's response has been more cautious than the administration might prefer. The Alliance for Automotive Innovation, which represents General Motors, Toyota, Volkswagen, and other major automakers, asked the EPA in September to roll back the Biden-era emissions limits but argued the agency should still rewrite the rules rather than eliminate them entirely. The group said revised standards "still need to be revised to feasible levels to provide certainty for the industry" and called for a contingency plan "if motor vehicle GHG standards are retained or reinstated in some way."

The American Petroleum Institute backed the repeal as it applies to vehicles but drew a line at stationary sources. API President Mike Sommers said in January that "we would not support repealing the endangerment finding for stationary sources," adding that the EPA clearly has authority to regulate greenhouse gas emissions from power plants and oil and gas facilities.

Car manufacturers have struggled in recent years to comply with increasingly strict tailpipe emissions caps. They have ramped up electric vehicle production, but many EVs have sat on dealer lots as consumers gravitated toward hybrids or less expensive gas-powered vehicles. Transportation remains the largest source of U.S. greenhouse gas emissions, accounting for roughly 28 percent of the national total.

Legal challenges ahead

Environmental groups have promised immediate litigation. The Natural Resources Defense Council called the repeal "the biggest attack ever on federal authority to tackle the climate crisis" and said its legal arguments "should be laughed out of court." The Environmental Defense Fund and Earthjustice have also pledged lawsuits.

Peter Zalzal, a lawyer and associate vice president at the Environmental Defense Fund, said the repeal "would put more deadly pollution in our air and hit Americans in their pocketbooks with higher insurance, gas, and healthcare costs." An Associated Press analysis from July estimated that the climate rules the EPA is targeting could prevent tens of thousands of deaths and save the U.S. $275 billion for each year they remain in effect.

Defending the repeal in court could easily consume the remainder of Trump's second term. A lengthy legal battle also carries risk for the administration: if courts ultimately strike down the repeal and leave the endangerment finding intact, a future Democratic president would be empowered to issue new climate regulations on an even stronger legal footing.

Roger Pielke Jr., a senior fellow at the American Enterprise Institute, offered a more measured assessment. "The practical effect of either rescinding or not rescinding the endangerment finding may be a lot less than most people wish it was," he said, noting the finding alone has not driven the most significant changes in how the U.S. produces energy.

Myron Ebell, who ran the EPA transition team during Trump's first term and has pushed for the repeal since 2009, disagreed. "This is the culmination of a lot of effort over a lot of time by a lot of people who didn't give up," he said.