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Where it came from and why it’s so important

The Trump Administration has been doing its best to reverse and undermine environmental policies since taking office. One of the most notorious of such actions, but also among the most complicated to appreciate, has been the proposed reversal of EPA’s endangerment finding.

On July 29, 2025, EPA announced proposed regulations to reverse rules published more than 15 years ago under the Clean Air Act. The original rules authorized issuance of standards to reduce greenhouse gas emissions (GHGs) if EPA determines such emissions threaten the public health and welfare of U.S. citizens — as commonly referred to, the “endangerment finding.” EPA Administrator Lee Zeldin proudly called the proposed July 29 regulations “the greatest and most consequential day of deregulation in the history of the United States”. Mainstream climate scientists and environmental groups immediately denounced the proposal pointing out the growing evidence that climate change is causing disasters around the globe. The proposal reflects the Trump Administration’s extreme hostility toward environmental protection in general and climate change in particular. If, as expected, the rules are finalized as proposed, litigation will immediately follow and become the focus of another major test of the Supreme Court’s loyalty to the Administration.

1. What exactly is the “endangerment finding”?

During the George W Bush presidency, EPA took the position that the Clean Air Act did not authorize regulations to address a global problem — only to protect U.S. residents. In response to litigation brought by 19 environmental groups and later joined by several states, the Supreme Court ruled against EPA in a 2007 decision, Massachusetts v. EPA. The Court concluded that greenhouse gases fit within the Act’s definition of “air pollutant” and observed that emissions from American motor vehicles were then more than 6% of the global total and that US emissions were a significant contributor to the problem:

“Considering just emissions from the transportation sector, which represent less than one-third of this country’s total carbon dioxide emissions, the United States would still rank as the third-largest emitter of carbon dioxide in the world, outpaced only by the European Union and China. Judged by any standard, U. S. motor-vehicle emissions make a meaningful contribution to greenhouse gas concentrations and hence, according to petitioners, to global warming.”

The Court further decided EPA’s asserted reasons for failing to regulate were inadequate to amount to a reasoned justification. (Notably, all five members of the majority have since retired, while three of the dissenting votes (Roberts, Thomas, and Alito) remain on the Court.)

In response to the Mass v. EPA decision, EPA issued the endangerment finding in 2009:

“The Administrator finds that the current and projected concentrations of the six key well-mixed greenhouse gases. . .in the atmosphere threaten the public health and welfare of current and future generations.”[1] The finding was the basis for regulations on GHG emissions from new motor vehicles and subsequently for coal burning power plants.[2]

2. How can EPA justify concluding that regulations to address climate change are not needed?

The dangers of unchecked climate change are increasingly apparent. The earth is getting warmer every year, higher temperatures are reducing labor productivity, increasing ocean temperatures, causing more rapid and larger hurricanes and intense rainfall events, and fear of Antarctic melting and disastrous sea level rise. Scientists have even raised the specter of mass extinctions comparable to those millions of years ago due to the rapid rate of growth in emissions.

The EPA justifies the proposed reversal of the endangerment finding by citing a new U.S. Department of Energy report authored by five climate scientists.[3] Each scientist was selected based on their rejection of the international consensus on the seriousness of climate change and skepticism regarding the need for climate action. As DOE summarized, “[T]he report concludes that CO2-induced warming appears to be less damaging economically than commonly believed, and that aggressive mitigation strategies may be misdirected. Additionally, the report finds that U.S. policy actions are expected to have undetectably small direct impacts on the global climate and any effects will emerge only with long delays.”

The report was trashed by mainstream climate scientists, most notably in a 135-page report published by the National Academy of Sciences. The Academy report was produced by a committee of 16 leading climate scientists in a matter of weeks in order to be within the deadline for comments on the proposed rule. The authors concluded “unequivocally” that climate change is harming the health and welfare of U.S. citizens — the central issue challenged in the DOE report. Another report organized by an NGO, Carbon Brief, surveyed climate scientists and compiled a list of more than 100 errors or misrepresentations. “I’m gobsmacked,” says Benjamin Santer, a climate scientist at the University of East Anglia in Norwich, UK, who spent three decades working at the DoE’s Lawrence Livermore National Laboratory in California. “It’s a revision of science and a revision of history. We have to respond.”[4]

A lawsuit filed in August by environmental groups also challenges the procedures DOE followed to create the report. The suit alleges that the Trump administration violated the law by secretly recruiting a group of people who reject the scientific consensus on climate change with the specific intent to produce a report downplaying the risks of inaction. The groups accuse DOE and EPA of “flagrant violations” of the Federal Advisory Committee Act of 1972 which requires that any groups developed to advise federal policy must be disclosed and that meetings, emails and other records be made public.

3. Why does the business community (with a few exceptions) oppose EPA’s proposed deregulation?

Most Trump Administration proposals to relax environmental regulation have been welcomed by business interests. The reaction to EPA’s proposed repeal of the “endangerment finding” is a striking exception. Unlike “drill, baby drill” and weakening of pollution standards, the proposal is opposed by most industry groups[5] for reasons that reflect the complex relationship of federal and state environmental laws. EPA’s regulation of GHG emissions has a lengthy legal history going back more than 20 years — it’s a complicated but important story and critical to understanding the continued significance of the endangerment finding.

In the years that followed the 2009 endangerment finding, business interests accepted the concept of federal climate regulations, if not always the industry specific standards. Companies saw benefits from a unform national policy and protection from an onslaught of litigation against them from state and local governments. The potential for such lawsuits is based on nuisance claims and violations of laws against misleading consumers. Preemption of such suits was confirmed by the Supreme Court in a 2011 decision, American Electric Power v. Connecticut. The Court concluded states could not bring suit based on federal common law because Congress had given EPA the authority to determine whether and how to regulate GHG emissions. The rationale in the AEP case has proven to be an effective defense by industry in many lawsuits brought by state and local governments against them for climate damages.[6] For example, a state court recently dismissed a claim brought by Charleston, South Carolina against oil and gas companies finding that such claims went far beyond state authority.

Without going so far as to reverse the endangerment finding, EPA has also shown a willingness to support industry through lax enforcement and multiple proposals to weaken federal regulations. Yet creating an opening for state and local regulation by removing federal climate rules (with few exceptions) has not been welcomed by industry. See, for example, criticism from the Edison Electric Institute (EEI) and Business Council for Sustainable Energy. [7] If EPA does not have the authority to regulate greenhouse gas emissions, an EEI official noted, “we would face a patchwork of state regulations and lawsuits from plaintiffs that could raise costs to customers and impact grid reliability.” While public, industry criticism of the proposed regulatory reversal has been relatively muted, no doubt reflecting the desire to avoid too open disagreement with the Trump Administration.

4. How can EPA claim it will protect business from state and local lawsuits?

EPA claims it can preempt state and local regulation based on its Clean Air Act (CAA) authority even if not exercised. “We are … aware that regulated parties may have reliance interests in national uniformity,” the EPA said in its proposal. But the agency said that although it determined that regulating greenhouse gas emissions “based on global climate change concerns” does not meet the requirements of the Clean Air Act, the EPA retained its authority to regulate those emissions in the future.[8]

Richard Revesz, dean emeritus of New York University School of Law, who served as a top regulatory official in the Biden White House, questioned EPA’s rationale. “EPA is trying to thread an impossibly small needle,” Revesz said. “They don’t want to regulate greenhouse gas emissions. And they also don’t want California to be able to have its own vehicle greenhouse gas emission standards, and they don’t want [federal common law actions] to come back to life. They want to have it both ways, and their ability to succeed is questionable.”[9]

Conclusion: The Trump Administration continues to promote its belief that climate change isn’t a threat in every possible way: cutting climate science programs; blocking U.S. participation in international climate meetings; taking down climate websites; rewriting climate reports, ending CO2 measurements and satellite data collection. The proposed repeal of the endangerment finding is yet more proof of its anti-science, facts be damned, ideological approach. While budget and program cuts have largely been accepted by the courts, the shocking assertion that climate change is no longer a threat to public health and welfare will be a critical test of judicial oversight. For if such an outrageous act is allowable, the rule of law is seriously in doubt.

[1] The Supreme Court left it to EPA to make the endangerment finding, thus creating the basis for EPA to now attempt to reverse it.

[2] Regulations to limit CO2 emissions from coal burning power plants were issued by the Obama EPA in 2015 were ruled illegal by the Supreme Court in 2022 (because they relied on fuel switching) and new ones promulgated by the Biden Administration in 2024. For a history leading up to the Trump Administration, see D. Lashof, “4 Things to Know About US EPA’s New Power Plant Rules” (WRI, May 3, 2024)

[3] The authors of the Department of Energy report were Steven E. Koonin, a physicist and author of a best-selling book that calls climate science “unsettled”; Judith Curry, a climatologist who has criticized climate activists for “alarmism” about warming; John Christy, an atmospheric scientist known for his doubts about the extent to which human activity has caused global warming; Roy Spencer, a meteorologist at the University of Alabama, Huntsville; and Ross McKitrick, an economics professor at the University of Guelph in Canada.

[4] A further reflection of attitudes toward the EPA proposal was reflected in the criticism aired at the first public hearing on August 19th. Roughly 200 testified, of whom fewer than 10 spoke in support.

[5] Zeldin announced the proposal at a car dealership in Indiana with the support of one industry group, the American Trucking Association.

[6] According to the NY Times, Roughly three dozen similar cases have been filed across the country since 2017 with three state supreme courts rejecting industry motions to dismiss.

[7] Representatives of the American Petroleum Institute expressed conflicting opinions first publicly opposing the regulations and subsequently expressing support at a public hearing — no doubt more a reflection of political loyalty than economic interest.

[8] There have also been some advocates for seeking reversal of the Supreme Court’s 2007 decision to prevent future EPA regulation. Should that happen, the door would be open for state and local regulation without question.

[9] The issue had been raised during the first Trump Administration. In a 2018 law review article, professors Nevitt and Percival discuss the whether federal preemption of state and local climate suits is legally possible. They concluded: “If the Trump EPA reverses the 2009 endangerment finding, this would foreclose the EPA’s ability to use the CAA to regulate GHG emissions. . . .While the Supreme Court ruled in AEP that the CAA displaces any federal common law right to seek abatement of carbon-dioxide emissions from fossil fuel fired power plants, this was predicated on EPA actually making a reasoned and informed judgment of GHG emission dangers — not jettisoning agency expertise in favor of politics. . . . But this is predicated on some form of occupation; a refusal to occupy the field is an abdication of responsibility.”

Alan Miller is a former climate change officer in the International Finance Corporation (2003–13) and climate change team leader, Global Environment Facility (1997–2003). Besides other engagements, Alan is an active editor for Climate Conscious submissions on Medium.