A coalition of US environmental and health groups has filed suit against the Trump administration's repeal of a key scientific finding that underpinned federal climate regulations.

The action, taken in a Washington appeals court on Wednesday, argues that President Donald Trump's move – which eliminated greenhouse gas standards on automobiles and placed a host of additional rules in jeopardy – was illegal.

Trump's Environmental Protection Agency (EPA) rejected the accusation, insisting in a statement that it had "carefully considered and reevaluated the legal foundation" of the finding.

The federal body said it concluded it did not have statutory authority to set automobile emissions standards "for the purpose of addressing global climate change concerns".

"Unlike our predecessors, the Trump EPA is committed to following the law exactly as it is written and as Congress intended – not as others might wish it to be," the agency said in the statement.

The 2009 "endangerment finding," which said greenhouse gases harm public health, was core to years of federal climate policy.

According to the coalition, the Trump administration's justifications for the repeal do not hold water and have already been litigated, with the Supreme Court reaffirming the endangerment finding multiple times – most recently in 2022. It's likely the issue eventually will land there once again.

The case was brought by a broad group of organisations including the American Lung Association, the Clean Air Council, the Union of Concerned Scientists, the Sierra Club and the Center for Biological Diversity.

"We're suing to stop Trump from torching our kids' future in favour of a monster handout to oil companies," said David Pettit, an attorney at the Center for Biological Diversity, in a statement.

"Nobody but Big Oil profits from Trump trashing climate science and making cars and trucks guzzle and pollute more," Pettit said. "The EPA's rollbacks are based on political poppycock, not science or law, and the courts should see it that way."

Trump, 79, has dismissed concerns that the repeal could cost lives by worsening climate change, reiterating his belief that human-caused global warming is a hoax.

The administration has framed the measure as a cost-saving move, claiming it would generate more than US$1 trillion in regulatory savings and bring down new car costs by thousands of dollars.

The endangerment finding was a determination based on overwhelming scientific consensus that six greenhouse gases threaten public health and welfare by fuelling climate change.

While it initially applied only to vehicle emissions, it later became the legal foundation for a broader suite of climate regulations, which are now vulnerable. (AFP)



Edited by Cecil Wong