Governors' Biofuels Coalition

A coalition led by California sued the Trump administration over car emissions rules on Tuesday, escalating a revolt against a proposed rollback of fuel economy standards that threatens to split the country’s auto market.

In a lawsuit filed in the United States Court of Appeals for the District of Columbia, California and its coalition — 17 other states and the District of Columbia — called the Environmental Protection Agency’s effort to weaken auto emissions rules unlawful and accused the agency of failing to follow its own regulations and of violating the Clean Air Act.

“States representing 140 million Americans are getting together to sue Outlaw Pruitt — not Administrator Pruitt, but Outlaw Pruitt,” Gov. Jerry Brown of California said at a news conference, speaking of the Environmental Protection Agency administrator, Scott Pruitt. “This is about health, it’s about life and death,” he said. “I’m going to fight it with everything I can.”

California has separately threatened to sue if the E.P.A. challenges a waiver granted by the Obama administration that allows the state to set its own greenhouse gas emissions regulations.

The state has long been authorized under the 1970 Clean Air Act to write its own stricter air pollution rules, and a dozen other states have traditionally followed those standards, which are designed to curb earth-warming emissions from cars and light trucks.

In 2012, when the Obama administration set a comprehensive set of standards on greenhouse gas emissions and fuel economy for cars and light trucks — aiming to roughly double the average fuel economy of new cars, S.U.V.s and light trucks by 2025 — California agreed to harmonize its own regulations with the new federal standards.

But last spring, executives from the Big Three automakers went to the White House to ask for more lenient emissions rules, kicking off an effort by the administration to roll back those standards. The E.P.A., together with the National Highway Traffic Safety Administration, has now drafted a new set of regulations that would dramatically weaken the Obama-era rules after 2020.

California had said it would stick with the tougher regulations, and had threatened to sue should Washington try to challenge its authority to follow its own air pollution rules. Tuesday’s lawsuit was seen as a pre-emptive move that calls the entire rollback unlawful.

A legal battle with California brings the nation’s auto industry closer to a split into two markets as its legal challenge plays out in court: one that continues to follow stricter rules requiring cars to be more efficient and less polluting than the other.

The 18 jurisdictions joining in Tuesday’s lawsuit represent more than 40 percent of the U.S. auto market, California said. According to its news release, they are: California, Connecticut, Delaware, District of Columbia, Illinois, Iowa, Maine, Maryland, Massachusetts, Minnesota, New Jersey, New York, Oregon, Pennsylvania, Rhode Island, Vermont, Virginia and Washington.

Automakers are scrambling to avert that outcome, urging for continued talks over a unified national program. They have asked for a direct meeting with President Trump to try to avert an all-out weakening of regulations that they fear will now go well beyond what they themselves initially sought, according to two people with knowledge of the automakers’ plans.

Separately, Senator Tom Carper of Delaware, the top Democrat on the Environment and Public Works Committee, sent a letter to the secretary of the Department of Transportation, Elaine Chao, and Mr. Pruitt asking that they abandon the rollback.

“Such a proposal, if finalized, would harm U.S. national and economic security, undermine efforts to combat global warming pollution, create regulatory and manufacturing uncertainty for the automobile industry and unnecessary litigation, increase the amount of gasoline consumers would have to buy, and runs counter to statements that both of you have made,” Senator Carper wrote. “ I urge you to immediately disavow this proposal.”