For years, the fossil fuel industry and its allies have tried to overturn one of the most important federal rulings in the history of climate policy: the one that requires the government to limit greenhouse gases.
They lobbied. They sued. And so far they’ve failed.
But in President Trump, they have a new ally in their campaign against the rule, known as the endangerment finding. The finding empowers the Environmental Protection Agency to regulate greenhouse gases, like carbon dioxide, because they endanger human life.
On his first day in the White House, Mr. Trump ordered the E.P.A. administrator and other agency leaders to make a recommendation within 30 days on the “legality and continued applicability” of the endangerment finding, setting up an early clash over the science of climate change.
Since the E.P.A. has an obligation to regulate pollutants that harm human health, eliminating the endangerment finding would debilitate the agency’s authority to curb emissions from automobile exhaust, power plants, oil and gas wells, factories and more.
“This is going to happen,” said Steven J. Milloy, a former Trump transition adviser, referring to the overturning of the endangerment finding. Mr. Milloy, who denies the established science of climate change and has been encouraging the new administration to reverse the finding, said that without it, “all the federal government climate stuff kind of melts away.”
Lee Zeldin, Mr. Trump’s pick for E.P.A. administrator, did not address the matter head-on during his confirmation hearing. In written answers to the committee, reviewed by The New York Times, he pledged to “learn from E.P.A. career staff about the current state of the science on greenhouse gas emissions and follow all legal requirements,” and said, “I acknowledge that there are many who endorse the endangerment finding and others who have concerns about it.”
Legal experts said the administration’s chances of successfully overturning the finding were slim. It was challenged in more than 100 lawsuits and was previously upheld by a federal appellate court. And as recently as 2023, the Supreme Court, with its majority of six conservative jurists (three appointed by Mr. Trump), declined to review the case.
“It’s a finding about greenhouse gasses based on science. It will be hard to convince a court — even a court with Republican-appointed judges — that the science somehow isn’t there to support this finding,” said Jody Freeman, director of the Environmental & Energy Law Program at Harvard Law School.
And in a notable shift, many of the staunchest corporate critics of the E.P.A.’s finding, as well as others who challenged it in court more than a decade ago, have abandoned the effort.
Over the past decades of record-breaking heat and weather disasters, businesses have become more aware of the risks to their bottom lines posed by global warming. Europe and other foreign markets also have moved to aggressively regulate carbon emissions, which means that American companies must plan for regulations even if they don’t apply in their home market.
Public opinion has also shifted significantly.
Evidence of climate dangers, already clear in 2009, is overwhelming in 2025 amid supercharged wildfires, droughts, floods and deadly heat waves. When the endangerment finding was issued, just 35 percent of Americans saw climate change as a serious problem, compared with more than 60 percent today.
“We are not calling for reversing the endangerment finding, which has been settled law for over a decade, as we believe that we can both unleash America’s energy potential and continue to reduce greenhouse gas emissions,” said Marty Durbin, president of the Global Energy Institute at the United States Chamber of Commerce.
That said, industry groups are eager to restrict the government from imposing regulations on their companies, and many support Mr. Trump’s agenda of weakening air and water protections. Few groups, however, are interested in a battle that would require them to publicly endorse Mr. Trump’s false claim that climate change is a hoax.
“I don’t think that’s an easy message for industry to embrace,” said Kyle Danish, a partner at Van Ness Feldman, a Washington law firm that advises energy clients. “They’re beyond the point where they can say greenhouse gases don’t endanger public health and welfare,” he said.
The endangerment finding was born out of a 2007 Supreme Court ruling in Massachusetts v. E.P.A. that stated that the Clean Air Act obligated the agency to address pollutants that harm public health indirectly by warming the planet. The ruling forced the agency to weigh in on whether six greenhouse gases harmed public health, which the agency did, in the affirmative, in 2009.
That assessment set off a legal mandate to regulate those emissions. To do so, the agency developed more than 200 pages of findings that outlined the science and detailed how increasingly severe heat waves, storms, floods and droughts were expected to contribute to higher rates of death and disease.
While President Trump’s election appears to have offered opponents of the endangerment finding their best new shot at ending the rule, any attempt to do so would be not only a gamble, but also perhaps an inefficient way to reduce government regulation.
The Edison Electric Institute, which represents some of the biggest electric utilities in the country, told the Supreme Court in 2023 that if the endangerment finding were overturned, power plants across the country could be exposed to lawsuits and a patchwork of decisions. “This would be chaos,” the group said.
Several attorneys who represent electric utilities and other energy companies said their clients had not expressed a desire to overturn the endangerment finding. “They want sensible regulatory reforms,” said Jeffrey R. Holmstead, an energy attorney with Bracewell, a Washington law firm.
Ms. Freeman noted that the first Trump administration did not seek to overturn the finding, despite calls for it to do so. Instead, it weakened existing rules and made enforcement a low priority, which led to legal challenges that were handled case by case. An overturning of the endangerment finding would allow the administration to stifle all greenhouse gas regulation in one fell swoop.
“That’s the big payoff for them, and why they might, for ideological reasons, for performative reasons, or because they calibrated the legal risk, say, ‘Let’s, let’s try it.’ You never know, with this Supreme Court, right?” Ms. Freeman said.
One possible avenue for the E.P.A. today would be to reprise arguments that failed to sway the court in 2007. None of the justices who voted in the 5-4 majority in the case are still on the court. The Trump administration could be betting that the court is more likely to favor their arguments this time around.
Nathan Richardson, a law professor at Jacksonville University, said that Massachusetts v. E.P.A. was a landmark decision that today’s court would most likely view very differently. But the goal of weakening regulations could still be achieved by the much easier strategies of inaction or lax enforcement. The administration may also believe there is a political benefit to arguing against the existence of climate change in court.
“Climate change, to many in the Trump administration, seems to be more of a culture-war issue than a science one,” Mr. Richardson said.
The administration could also seek to weaken E.P.A. regulations in other ways, rather than in a central assault on the endangerment finding, he said. “There’s plenty of vehicles to do that — this would just be a particularly high-profile and brazen one,” he said.
“Normally that’s not a good litigation strategy. But maybe strategy is different when you feel like the court is really, really on your side.”
