The Trump administration and Republicans in Congress are preparing an unusual legislative maneuver in an effort to eliminate one of the country’s most ambitious climate policies, an order that was designed to shift the auto industry toward electric cars.

They plan to vote to overturn a California ban on the sale of new gasoline-powered cars in that state by 2035. To do it, they intend to use the Congressional Review Act, a 1996 law that permits lawmakers to reverse recently-adopted regulations with a simple majority vote.

But the California ban is not a federal regulation. It’s the result of a waiver that was granted by the Biden administration under the 1970 Clean Air Act, something that has been done more than a hundred times over the years by administrations of both parties. And it is not subject to congressional review, according to a 2023 decision by the Government Accountability Office.

Environmental groups and California officials say the Republican plan to try to kill the waiver with a congressional vote would be illegal.

Gov. Gavin Newsom of California, a Democrat who frequently sparred with Mr. Trump during the president’s first term and who has promoted his state as an environmental leader, declined to comment. His office referred questions to the state’s air pollution regulator, the California Air Resources Board.

David Clegern, a spokesman for the board, said in a statement, “The Trump E.P.A. is doing what no E.P.A. under Democratic or Republican administrations in 50 years has ever done, and what the G.A.O. has confirmed does not comply with the law.”