California Attorney General Rob Bonta is co-leading a nationwide lawsuit against the U.S. Environmental Protection Agency over its rescission of a finding on greenhouse gases.

The 2009 Endangerment Finding was the federal government’s recognition that the gases threaten public health and welfare. The finding also provided the legal basis for regulating emissions from motor vehicles, power plants and industry under the Clean Air Act.

“It’s grounded in science, it’s been upheld by the courts, and some would just refer to it as common sense,” said Bonta during a Thursday morning press conference announcing the lawsuit. “Now President Trump and his EPA are trying to erase it entirely.”

President Donald Trump has referred to climate change as a “hoax.” Trump is also on record as saying green policies harm consumers and the economy, and the EPA says the new lawsuit is motivated by politics.

Plaintiffs say it's motivated by environmental concerns.

“The federal government is attempting to overrule the science and do away with the protections that limit harmful pollution from vehicles, the largest source by the way, of greenhouse gas emissions in the United States,” said Bonta, who boasted about this being the 63rd lawsuit California has filed against the Trump administration in 63 weeks. Bonta is joined in the suit by Democratic attorneys general and other Democrats from states throughout the U.S.

California Gov. Gavin Newsom, a Democrat who's a frequent critic of the president and is widely expected to run for president in 2028, joined Bonta for the “Trump Is Making Deadly Pollution Great Again” press conference.

Newsom said the last decade between 2015 and 2025 was the hottest one in history as the world deals with climate change. The Southwest is undergoing a heat wave that is bringing unseasonal triple-digit temperatures this week.

“There’s no Republican thermometers; there’s no Democratic thermometers,” said Newsom. “If you don’t believe in science, you've got to believe your own eyes."

According to Newsom, places, lifestyle and traditions are “being quite literally wiped away.”

He pointed to Paradise, Grizzly Flats, and Greenville, Calif., as examples. Newsom and others believe climate change played a role in the fires that damaged those areas.

By repealing the Endangerment Finding, California Air Resources Board Chair Lauren Sanchez said the Trump administration is abdicating its responsibility to protect Americans.

“California is not going to sit back and watch while the federal government dismantles critical public health protections,” said Sanchez. “We are going to fight back.”

The federal lawsuit is filed in the U.S. Court of Appeals for the Washington, D.C. circuit.

The EPA Thursday told The Center Square, “It is revealing that the plaintiff-states ran to the press before even filing their complaint.” The EPA added that this illustrates that, for them, this is not about the law or the merits of any argument. According to the EPA, the plaintiffs are clearly motivated by politics.

“EPA carefully considered and reevaluated the legal foundation of the 2009 Endangerment Finding, the text of the CAA, and the Endangerment Finding’s legality in light of subsequent legal developments and court decisions,” the EPA press office said. “This included a robust analysis of the law following the U.S. Supreme Court decision in Loper Bright Enterprises v. Raimondo and West Virginia v. EPA.”

The agency concluded that Section 202(a) of the CAA does not provide EPA statutory authority to prescribe motor vehicle emission standards for the purpose of addressing global climate change concerns.

“In the absence of such authority, the Endangerment Finding is not valid, and EPA cannot retain the regulations that resulted from it. EPA is bound by the laws established by Congress, including under the CAA,” said the EPA press office. “Congress never intended to give EPA authority to impose GHG regulations for cars and trucks.”

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

Pennsylvania Gov. Josh Shapiro, a Democrat, also joined the lawsuit along with the cities of Boston, Chicago, Cleveland, Columbus (Ohio), Denver, Los Angeles, New York City, San Francisco, Santa Clara and Harris County, Texas.

Bonner Cohen, a senior fellow at the Committee for a Constructive Tomorrow, thinks the suit will end up at the U.S. Supreme Court.

“I suspect the Supreme Court will uphold what the EPA is proposing to do because nowhere in the CAA does it say specifically that the EPA is authorized by Congress to regulate greenhouse gas emissions,” Cohen told The Center Square Thursday. “The language there is very vague, and the current Supreme Court has been very particular in saying that regulatory agencies cannot make regulations up out of whole cloth. They must have specific congressional authorization to exercise their power, and the EPA administrator recognizes that his agency does not have that power.”