WASHINGTON — The Trump administration is expected on Wednesday to formally revoke California’s authority to set auto emissions rules that are stricter than federal standards, taking a major step forward in its wide-ranging attack on government efforts to fight climate change.
The formal abolishment of one of California’s signature environmental policies — tailpipe pollution is the largest source of greenhouse gas emissions in the United States — will be announced Wednesday afternoon at the Washington headquarters of the Environmental Protection Agency, according to two people familiar with the matter. Mr. Trump at the time will be traveling in California, where he is scheduled to attend fund-raisers in Los Angeles and Silicon Valley.
Lawyers said the action takes the administration into uncharted legal territory in its battle with the state, which has vowed to fight the change all the way to the Supreme Court.
“This is unprecedented and a tremendously big deal,” said Richard L. Revesz, a professor of environmental law at New York University, noting that no administration has ever revoked a state’s authority to regulate its own air quality in the past.
In a speech on Tuesday, Andrew Wheeler, the head of the E.P.A., said, “We embrace federalism and the role of the states, but federalism does not mean that one state can dictate standards for the nation.”
The attack on California is only the latest in a broad array of efforts to weaken climate change regulations by a president who has repeatedly expressed skepticism about the scientific consensus that global warming is human-caused. The administration plans to weaken auto emissions standards nationwide, has rolled back rules governing coal-burning power plants and eased restrictions on energy companies governing leaks of methane, a powerful greenhouse gas.
A revocation of the California waiver would have national significance. Thirteen other states follow California’s tighter standards, together representing roughly a third of the national auto market.
Legal experts said that if Mr. Trump’s move was ultimately held up by the Supreme Court, it could permanently block states from regulating vehicle greenhouse gas pollution. If it was rejected by the Supreme Court, it would allow states to set separate tailpipe pollution standards from those set by the federal government.
The outcome could split the United States auto market, with some states adhering to stricter pollution standards than others. For automakers, that would be a nightmare.
Opponents of the move noted that weakening California’s authority on emissions is directly at odds with the administration’s position on other vital issues — such as gun restrictions and abortion laws — that individual states have the right to set their own rules. “Trump has married his administration-wide hostility to the environment to his personal vendetta against California,” said Dan Becker, director of the Safe Climate Campaign, an advocacy group.
A spokesman for the E.P.A. did not respond to an email requesting comment. In his speech to the National Automobile Dealers Association, Mr. Wheeler said the administration would soon be moving ahead with a single national vehicle pollution standard, suggesting that it would include the California revocation.
The move has been widely expected since last summer, when the Trump administration unveiled its draft plan to roll back the strict federal fuel economy standards put in place by the Obama administration. That draft Trump rule also included a plan to revoke the state’s legal waiver — granted to California under the 1970 Clean Air Act — allowing it to set tougher state-level standards than those put forth by the federal government.
Xavier Becerra, the attorney general of California, said the state intends to strike back with a lawsuit. “While the White House clings to the past, automakers and American families embrace cleaner cars,” he wrote in an email. He called the tougher standards “achievable, science-based, and a boon for hardworking American families and public health.”
In recent months, the administration’s broader weakening of nationwide auto-emissions standards has become plagued with delays as staff members struggled to prepare legal, technical or scientific justifications for it. As a result, the White House decided to proceed with just one piece of its plan — the move to strip California of its authority to set tougher standards — while delaying its wider strategy, according to these people.
The administration’s plans have been further complicated because major automakers have told the White House that they do not want such an aggressive rollback. In July, four automakers formalized their opposition to Mr. Trump’s plans by signing a deal with California to comply with tighter emissions standards if the broader rollback goes through.
Mr. Trump, who was blindsided and angered by that announcement, according to two people familiar with the matter, wanted to press forward with a policy that would punish California.
“It’s clear that the president felt very strongly about this,” said Thomas J. Pyle, the president of the Institute for Energy Research, a think tank that supports fossil fuels, who advised Mr. Trump’s 2016 campaign. “The actions of California and the other auto companies probably firmed up or hardened the president’s resolve on this issue, so here we go.”
The Obama-era tailpipe pollution rules that the administration hopes to weaken would require automakers to build vehicles that achieve an average fuel economy of 54.5 miles per gallon by 2025, cutting about six billion tons of carbon dioxide pollution over the lifetimes of those vehicles. The proposed Trump rule would lower the requirement to about 37 miles per gallon, allowing for most of that pollution to be emitted.
White House officials have been eager to move quickly to revoke California’s authority to set its own standards because they want the opportunity to defend the effort in the Supreme Court before the end of Mr. Trump’s first term. The thinking goes that if a Democrat were to be elected president in 2020, the federal government would be unlikely to defend revocation of the waiver in the high court.
California’s special right to set its own tailpipe pollution rules dates to the 1970 Clean Air Act, the landmark federal legislation designed to fight air pollution nationwide. The law granted California the right to receive federal waivers to set stricter rules of its own because the state already had clean air legislation in place before it passed.
Over the decades, California requested and received numerous federal waivers to set tighter state-level standards on the tailpipe pollutants that cause smog and respiratory problems, though the federal government didn’t always grant them.
The waiver in effect now was crafted in the wake of the 2008 financial crisis, when the nation’s automakers were financially teetering. It was part of a deal struck by President Barack Obama to toughen emissions standards nationwide while aligning California’s rules with federal regulations. It was designed to remain in effect until 2025.
For more news on climate and the environment, follow @NYTClimate on Twitter.