LOS ANGELES — California is suing the Trump administration over its decision to roll back the endangerment finding, the U.S. government’s longstanding scientific conclusion that planet-heating pollution seriously threatens Americans, state officials announced Thursday.

Attorney General Rob Bonta, Gov. Gavin Newsom and the California Air Resources Board are co-leading a coalition of 25 attorneys general, the governor of Pennsylvania, and 10 cities and counties in a petition challenging the Environmental Protection Agency, filed in the U.S. Court of Appeals for the D.C. Circuit.

The 2009 endangerment finding was a long-awaited, foundational piece of the nation’s effort to address climate change, and it underpinned much of U.S. climate policy — including the EPA’s ability to regulate greenhouse gas emissions from vehicles.

EPA Administrator Lee Zeldin touted the February repeal as “the single largest act of deregulation in the history of the United States of America.”

The coalition has argued that rescinding the endangerment finding is a violation of settled law, including clear Supreme Court precedent, as well as broad scientific consensus over the effects of greenhouse gas emissions on human health and welfare. Its rollback will disrupt the regulatory landscape and result in significant increases in greenhouse gas emissions, which drive climate change, they said.

The lawsuit will ask the court to vacate the EPA’s repeal and restore greenhouse gas emission standards for vehicles. A formal complaint is pending the judge’s acceptance of the petition.

“With the unlawful rescission of the Endangerment Finding, President Trump and his EPA have abandoned their most important mission: protecting the health and welfare of the American people,” Bonta said in a statement. “The science doesn’t lie: Climate change and [greenhouse gas] emissions are harming public health and causing devastating and ever-worsening disasters. Our communities have felt the impact of destructive wildfires, watched families run from burning homes, inhaling toxic fumes, and we’ve seen entire communities wash away in severe floods. The President can’t keep his head in the sand — climate change is real and decades of settled science warned us this was coming.”

Much of the EPA’s argument for repealing the endangerment finding hinged on whether greenhouse gases qualify as “air pollutants” under the Clean Air Act, making them subject to federal regulations. A landmark 2007 Supreme Court case, Massachusetts vs. EPA, determined that they are.

In its decision, the agency said it “carefully considered and reevaluated the legal foundation” for the finding and concluded that the Clean Air Act does not provide statutory authority for the agency to prescribe motor vehicle and emissions standards, and therefore has no legal basis for the endangerment finding or its resulting regulations.

In a statement Thursday, EPA officials reaffirmed that conclusion and said the lawsuit is not about the legality or the merits of their argument, but rather political motivation.

“EPA is bound by the laws established by Congress, including under the [Clean Air Act],” the agency said. “Congress never intended to give EPA authority to impose [greenhouse gas] regulations for cars and trucks.”

The coalition alleges that the repeal of the endangerment finding violates the Clean Air Act as well as the Administrative Procedure Act by resting on the “flawed assertion” that it lacks legal authority to regulate greenhouse gas emissions, and “ignores overwhelming and longstanding scientific evidence” about the role of greenhouse gas emissions on human health and welfare.

It also argues that the elimination of existing and future greenhouse gas emission standards for vehicles violates EPA’s legal obligations and fundamental responsibility to protect the public from environmental harm.

EPA’s repeal will not only disrupt 15 years of regulatory progress, but will also threaten American investment in future technologies and U.S. leadership in the transportation sector and efforts to address climate change, the coalition said.

“This is what corruption looks like. Donald Trump is breaking the laws that protect Americans from climate pollution — all to enrich his Big Oil and his wealthy polluting allies,” Newsom said in a statement. “Workers, families, and communities would pay the price, left choking on dirty air. No one is above the law in this country. Not even the president.”

The EPA also cast doubt on the climate science behind the endangerment finding, despite the fact that independent researchers around the world have long concluded that greenhouse gases released by the burning of gasoline, diesel and other fossil fuels are warming the planet and contributing to worsening climate impacts. Understanding of how carbon dioxide warms the atmosphere goes back more than a century.

Among its justifications, the agency’s ruling says that reducing greenhouse gas emissions from new and existing vehicles in the U.S. would have only “de minimis impacts” on global temperature and sea level rise. But many experts say reducing those emissions is critical for curbing climate change, as the transportation sector is the largest source of greenhouse gas emissions in the U.S. In California, it accounts for about half of the state’s emissions.

EPA’s proposal to repeal the endangerment finding received more than half a million public comments, including from environmentalists, scientists, civil rights groups, public health organizations and former EPA officials opposed to the plan. Support for the plan generally came from industry and regulatory reform groups who said the vehicle standards that rest on the endangerment finding are costly and unduly burdensome.

Bonta co-leads the lawsuit alongside the attorneys general of Massachusetts, New York and Connecticut. They are joined by attorneys general of Arizona, Colorado, Delaware, Hawaii, Illinois, Maine, Maryland, Michigan, Minnesota, New Jersey, New Mexico, Nevada, North Carolina, Oregon, Rhode Island, Vermont, Virginia, Washington, Wisconsin and the District of Columbia.

The coalition also includes Pennsylvania Gov. Josh Shapiro; the cities of Boston, Chicago, Cleveland, Columbus, Denver, Los Angeles, New York, San Francisco, Santa Clara and Harris County, Texas.

This marks California’s 63rd lawsuit against the Trump administration since the president returned to office last year.

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