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.

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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.