Trump has revoked a foundational scientific ruling that greenhouse gases are a threat to public health, demolishing the legal underpinning of the Environment Protection Agency’s (EPA) authority to act on climate change under the Clean Air Act. 

The landmark ruling was published by the EPA in 2009 under Obama. It has served as the linchpin of US greenhouse gas regulation – from auto exhaust standards to caps on emissions from power plants. 

Trump’s administration has made previous attempts to repeal many of these climate regulations, but this latest move could prevent future presidents from reestablishing any regulations to combat climate change. 

Environmentalists have called it one of the most significant rollbacks on climate change attempted by the legislation, and they are set to challenge it in the courts.

‘This is a big one if you’re into environment [sic],’ President Trump said yesterday at the White House.

He added the move would eliminate $1.3 trillion in regulatory costs, and would cause car prices to come ‘tumbling down. Trump provided no evidence behind these claims, and many environmental groups are sceptical of these cost savings. 

He described prior climate regulations as a ‘green new scam’ and blamed them for blackouts and inflation.

‘That’s all dead, gone, over,’ he said.

In mid-2025, Trump commissioned a report from a five member Climate Working Group which challenged the scientific consensus on human-caused climate change. The report suggested much of the observed warming is due to natural cycles rather than fossil fuel combustion and stated that sea-level rise is not accelerating.

More than 85 climate scientists submitted a report to the EPA detailing errors in the Climate Working Group’s report – and a federal judge ruled that the CWG committee was formed illegally since it operated in secrecy without public oversight or proper peer review.

It is unclear whether the Trump administration will try to lean on this report, but either way the contest in court over the repeal will be high stakes.

Former President Barack Obama, infrequently comments on the policies of sitting presidents, but said that: “Without it, we’ll be less safe, less healthy and less able to fight climate change – all so the fossil fuel industry can make even more money,” he wrote on X.

Many legal experts believe that the Trump Administration is actually looking for the repeal to be  tested in the Supreme Court before Trump’s term ends, believing that if they win, the endangerment finding will be consigned to history.

In the 17 years since the EPA ruled on the effect of greenhouse gas emissions on the public, the scientific documentation, and understanding of climate change has developed significantly. And it’s this resource bank of knowledge which could make Trump’s path to victory more difficult. 

However it could fall down to a legal technicality: whether the court decides the case based on the weight of that scientific evidence, or on the “Major Questions Doctrine,” which questions if the EPA ever had the statutory authority from Congress to regulate such a significant sector of the economy in the first place.

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