By rolling back a bedrock climate legal determination, the Trump administration has undercut its attacks on a groundbreaking state climate accountability law, green groups have argued in court.

Trump’s justice department has asked a judge to kill a first-of-its-kind 2024 Vermont “climate superfund” policy requiring major polluters to pay for damages caused by their past planet-heating pollution, partly on the grounds that that federal law, not state law, governs greenhouse gas emissions. But last month, Trump’s Environmental Protection Agency (EPA) repealed the endangerment finding, the scientific determination giving federal officials the authority to control those very pollutants.

“They’re trying to talk out of both sides of their mouths,” said Kate Sinding Daly, senior vice-president for law and policy at the environmental legal non-profit Conservation Law Foundation (CLF).

The administration cannot claim the federal government’s ability to enact greenhouse gas regulations precludes states’ authority to pass climate superfund laws while claiming it has no statutory authority to regulate emissions, CLF and advocacy group Northeast Organic Farming Association of Vermont asserted in a recent filing in federal court meant to defend Vermont’s climate superfund law. (Both the EPA and the Department of Justice declined to comment on the new filing.)

“We believe the rescission of the endangerment finding was wrong, that they were wrong to claim they don’t have the authority to regulate greenhouse gases,” said Daly. “But if they are going to say that, that then they can’t possibly preempt states from stepping in to do the same thing.”

It’s an argument legal experts anticipated would be made in the wake of the final endangerment finding repeal, and one that could also apply to defenses of the dozens of climate lawsuits filed by cities and states against big oil.

“I expect that the revocation of the endangerment finding will play a prominent role in countering the preemption claim in all these cases,” said Michael Gerrard, the founder of Sabin Center for Climate Change Law at Columbia Law School.

A similar line of reasoning appeared in a letter filed with a federal court on Tuesday by Letitia James, the New York attorney general, defending both Vermont’s policy and a climate superfund law passed by New York last year.The EPA and Department of Justice declined to comment on the letter.

EPA has claimed its endangerment finding repeal applies only to motor vehicle emissions. It has also said that the Clean Air Act “continues to preempt” state greenhouse gas laws and regulations, regardless of the endangerment finding repeal.

“The Clean Air Act preempts states and political subdivisions from adopting or attempting to enforce emission standards for new motor vehicles and engines, full stop, whether EPA has issued standards for particular emissions or not,” an agency spokesperson told the Guardian last month.

But Daly and other climate and legal experts say the agency’s final rule also removed the authority for the federal government to control greenhouse gas pollution from stationary sources such as power plants and fossil fuel facilities, removing the possibility that federal law precludes state regulations on any sector.

Even with the endangerment finding in place, states should legally be able to regulate greenhouse gases from any source, said Daly.

“In fact, we had prior administrations regulating greenhouse gas emissions from vehicles and proposing rules regulate the power sector, at the same time as we had states [also requiring] emission reductions,” she said.

And Vermont’s climate superfund should never have been considered preempted by federal law because it does not directly attempt to control future emissions, only to place costs on past emissions, said Daly. But the repeal of the endangerment finding should make it especially difficult for the preemption argument to stand up in court, she added.

“The argument is diametrically opposed to the argument in the endangerment finding repeal,” she said.

Grace Oedel, the executive director of Northeast Organic Farming Association of Vermont, said the stakes of the fight to protect climate superfund laws are high.

“It’s becoming increasingly clear that leaders in our federal government do not have a coherent plan for adapting to the climate crisis,” she said. “Farmers are bearing the weight of extreme weather events, and it’s fair for fossil fuel companies to help pay for the cost of climate adaptation.”

A livestreamed hearing about the DoJ’s attacks on Vermont’s climate superfund law will take place on 30 March.

Modeled after the EPA’s superfund program, which requires companies to pay for toxic waste cleanup, the climate superfund laws passed by Vermont and New York charge major fossil fuel companies for damages caused by their past emissions.

Other states, including Connecticut, Maine, Rhode Island, New Jersey and Illinois, are considering similar policies.

The potential impact of the endangerment finding on fossil fuel allies’ preemption arguments could also ripple through climate accountability litigation, including the dozens of suits brought by cities and states accusing major oil companies of climate deception. Last month, the supreme court agreed to hear a petition from energy producers seeking to dismiss one such case brought by Boulder, Colorado, arguing that federal law should preempt the claims.

Environmental and public health groups have sued the EPA over its repeal of the endangerment finding. The states of California and Connecticut have also pledged to bring lawsuits over the rollback.