WASHINGTON — The Trump administration is expected on Wednesday to formally revoke California’s legal authority to set tailpipe pollution rules that are stricter than federal rules, in a move designed by the White House to strike twin blows against both the liberal-leaning state that President Trump has long antagonized and the environmental legacy of President Barack Obama.
The announcement that the White House will revoke one of California’s signature environmental policies will come while Mr. Trump is traveling in the state, where he is scheduled to attend fund-raisers in Los Angeles and Silicon Valley.
The formal revocation of California’s authority to set its own rules on tailpipe pollution — the United States’ largest source of greenhouse emissions — will be announced Wednesday afternoon at a private event at the Washington headquarters of the Environmental Protection Agency, according to two people familiar with the matter.
A White House spokesman referred questions on the matter to the Environmental Protection Agency. A spokesman for the E.P.A. did not respond to an email requesting comment.
Xavier Becerra, the attorney general of California, wrote in an email: “California will continue its advance toward a cleaner future. We’re prepared to defend the standards that make that promise a reality.”
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 a legal waiver, granted to the state of California under the 1970 Clean Air Act, allowing it to set tougher state-level standards than those put forth by the federal government.
The revocation of the waiver would also affect 13 other states that follow California’s clean air rules.
In recent months, the administration’s broader weakening of nationwide auto-emissions standards has become plagued with delays as staff members struggled to prepare adequate legal, technical or scientific justifications for the move.
As a result, the White House decided to proceed with just one piece of its overall plan — the move to strip California of its legal authority to set tougher standards — while delaying the release of its broader rollback, 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.
While the broader efforts to undo the federal vehicle emissions standards remain incomplete, the legal proposal to revoke California’s legal authority to set its own pollution rule has been completed and ready to go for weeks.
White House officials have also been eager to move quickly to revoke California’s authority to set its own standards because they want the opportunity to defend the legal effort to undo emissions regulations 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 a waiver to set stricter rules of its own because the state already had clean air legislation in place before the landmark 1970 federal legislation.
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.
Because of that, the fight over federal auto emissions rules has the potential to split the United States auto market, with some states adhering to stricter pollution standards than others. For automakers, that represents a nightmare scenario.
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.
For more news on climate and the environment, follow @NYTClimate on Twitter.