Trump’s Repeal of Climate Tool Deepens Vehicle Emissions Fight

The Trump administration’s repeal of the endangerment finding that allows EPA to regulate greenhouse gas emissions throws another complicated factor into ongoing lawsuits over vehicle emissions standards, which have served as incentives to make and sell electric vehicles.

There are several US Supreme Court decisions that set the parameters around whether the Clean Air Act allows the regulation of greenhouse gases, who can challenge emissions standards, and what deference agencies have when interpreting the scope of their power.

The federal government will have to navigate these legal factors—which also include preemption issues with states—when defending decisions that weaken systems meant to encourage electric vehicle growth.

“The reduction of the federal emissions standards and the elimination of California’s ability to be more ambitious—those two measures in combination would have the effect of substantially reducing what’s required of manufacturers to produce and sell EVs in this country,” said Ted Lamm, associate director of University of California Berkeley’s Center for Law, Energy, and the Environment.

On the other hand, “it’s possible that the courts will find that this action allows states to do what California has previously needed permission to do,” he said.

Deregulation’s Legal Effects

Emissions regulations are intrinsically linked with the types of cars seen on the road each day. When the EPA rolled back the endangerment finding, it also repealed greenhouse gas emission standards for on-highway vehicles and engines.

“Transportation emissions are now the largest source of greenhouse gases in the United States, and this has been an area that has been tougher to drive emissions down in, as compared to the electricity sector,” said Ann Carlson, former acting administrator of the National Highway Traffic Safety Administration.

More internal combustion engine vehicles on the road means more emissions, smog, cardiorespiratory issues, and asthma, said David Pettit, senior attorney at the Center for Biological Diversity, an environmental advocacy group.

The group is among several challenging the EPA’s Feb. 12 decision finalizing its rescission of the 2009 endangerment finding, which established that greenhouse gases are a threat to public health. The group is separately suing over one of the many changes to the Corporate Average Fuel Economy Program proposed by the Trump administration.

The endangerment decision follows President Donald Trump’s other efforts to undermine electric vehicles. He has clawed back funding programs and tax incentives, rolled back fuel economy regulations, and eliminated civil penalties for those standards. All of these endeavors have been or are currently being challenged in court with varying degrees of success.

One of the legal hurdles the administration must contend with is the 2007 Supreme Court case, Massachusetts v. EPA, which found the EPA has the authority to regulate greenhouse gases as air pollutants under the Clean Air Act.

That meant EPA had the sole authority to set such standards, which preempt state regulations. In light of the endangerment finding repeal, the agency argues that if it doesn’t have the authority to regulate greenhouse gas emissions, neither do the states.

“The endangerment finding is basically, in my view, asking the Supreme Court to revisit Massachusetts versus EPA,” Carlson said.

“If greenhouse gases aren’t pollutants under that section of the act, as the administration is trying to argue, then it seems to me to leave a big open question about whether states can step in and regulate,” she said.

Manufacturers may not like that possibility because “automakers don’t want there to be 50 states with dozens of different kinds of standards,” Lamm said.

The EPA’s decision also contravenes another Supreme Court decision: Loper Bright Enters. v. Raimondo in 2024, which overturned deference to a federal agency’s interpretation of an ambiguous statute.

“Now the agency is saying states are preempted even though we’re not regulating,” Carlson said. “They’re not entitled to any deference.”

California As Ground Zero

The issue will affect whether states can establish their own greenhouse gas emission regulations since their only options currently are to follow EPA’s standards or California’s. The state was granted waivers under former President Joe Biden allowing it to set more stringent automobile pollution standards than those required by the federal government.

More than a dozen states follow California’s standards, but Trump signed three Congressional Review Act resolutions to revoke those EPA waivers in June. That also effectively got rid of California’s initiative mandating the sale of zero-emission vehicles over the next decade. California and other states launched a lawsuit challenging the CRA move.

The Supreme Court in 2025 ruled in Diamond Alternative Energy LLC v. EPA that fuel producers have standing to challenge California’s stringent vehicle emissions standards. That provides a window for entities wanting to get rid of California’s regulations, but it’s still unclear if the CRA will be upheld by courts as an appropriate method for doing so.

The states in the lower court decision that the high court overturned made “what I thought was a really nutty argument that the special treatment of California in the Clean Air Act was unconstitutional under the doctrine of equal sovereignty,” Pettit said.

“I view that as another attack on climate change regulations,” he said.

The issue of whether the CRA can be used to get rid of California’s waivers is currently pending before the US Court of Appeals for the Ninth Circuit. More than a dozen states, corn-growing associations, and fossil fuel groups will be watching to see what the appellate court decides and if a ruling would be petitioned before the Supreme Court.

The Congressional Review Act allows Congress to execute and the president to sign a repeal of federal rules and regulations.

However, “the waiver and the issuance of that waiver by EPA are not a rule or regulation” so “most legal experts who approach this honestly think that this is actually sort of an extra legal or ineffectual step,” Lamm said.