Nation & World
How Supreme Court may get chance to re-examine landmark climate ruling

Alvin Powell

Harvard Staff Writer

September 17, 2025 7 min read

Legal scholars say justices could reverse decision allowing EPA to regulate greenhouse gas emissions on technical grounds amid shift in court makeup

The Supreme Court is expected to get a chance to take a second look at a landmark 2007 decision that paved the way for federal regulation of greenhouse gas emissions from motor vehicles, power plants, and other sources.

But this time, legal scholars say, a shift in the makeup of the court may lead to a much different outcome, one that could have far-reaching implications for the nation’s battle against climate change. And the decision could have much more to do with technical legal arguments than the validity of the prevailing science.

“There were five justices to four justices” in Massachusetts v. Environmental Protection Agency, said Richard Lazarus, the Charles Stebbins Fairchild Professor of Law at Harvard Law School. “How many of those five justices are still on the Supreme Court? Zero. The majority is gone. And of the four, three are still there.”

The issue emerged in late July when current EPA administrator Lee Zeldin unveiled a proposed rule that would rescind what is called the endangerment finding, a step that would essentially revoke the agency’s authority to regulate activities that contribute to climate change under the Clean Air Act.

The finding has its roots in a 2007 case filed by Massachusetts along with some other states, cities, and environmental organizations, to force the administration of George W. Bush to regulate greenhouse gas emissions from automobiles.

The high court decision did not order the EPA to act but ruled that it had the authority to regulate greenhouse gases under the Clean Air Act.

That ruling cleared the way for Obama EPA administrator Lisa Jackson, in 2009, to officially find that greenhouse gases endangered human health and welfare.

That endangerment finding provided the legal underpinnings of subsequent efforts to cut climate change-causing emissions from motor vehicles and, by extension, power plants and other sources.

“They started with vehicles, but the endangerment finding is the touchstone for all Clean Air Act regulation by the EPA,” said Lazarus. “The same arguments you give for motor vehicles would apply for endangerment findings upon which all the other EPA regulations of greenhouse gases are based.”

“The same arguments you give for motor vehicles would apply for endangerment findings upon which all the other EPA regulations of greenhouse gases are based.”

Richard Lazarus

Zeldin’s move is just the latest in the push by the administration to loosen regulation aimed at climate change action, said Carrie Jenks, executive director of Harvard Law School’s Environmental and Energy Law Program.

“They’re going after the rules regulating various sectors and repealing those standards. They’re trying to undercut the market — like you’re seeing with wind farms — creating a lot of uncertainty and trying to stop construction,” Jenks said. “They’re trying to force coal plants that are uneconomic to continue to operate, which changes the market dynamic within the energy industry. And they’re threatening to attack states’ authority to regulate their own sources within their own states.”

Zeldin made his announcement at an Indianapolis auto dealership on July 29, saying the step would remove regulations, including the Biden administration’s electric vehicle mandate, that Zeldin said collectively cost industry $1 trillion — a figure that some climate-action supporters dispute — and make cars and trucks less affordable.

The Department of Energy released a report on the impact of greenhouse gases on the U.S. climate on the day of Zeldin’s announcement. That analysis argued that climate models overstate observed and future emissions trends and the future warming they’ll cause. It says those models don’t give enough due to natural variability and other, nonhuman, causes of rising global temperatures.

It also finds that U.S. attempts to curb emissions would result in “undetectably small” impacts on the global climate that would emerge only over a long time frame.

The government analysis was rebutted in a comment report by a group of 85 U.S. and international scientists. They argued that those claims are at variance with the wider scientific consensus that human activity has worsened climate change and that global warming is accelerating with increasingly destructive effects.

“They’re arguing in their primary proposal that this is the best and only reading of the Clean Air Act, which would say a future administration could not do something different.”

Carrie Jenks

Despite the scientific back and forth, the science may wind up not mattering much, Lazarus said.

That’s because the administration’s first arguments revolve around points of law that echo the dissents in 2007 (one was written by Chief Justice John Roberts, joined by Justices Clarence Thomas and Samuel Alito) and that today’s Supreme Court might find sufficient to overturn the original ruling.

Before the proposed rule even gets to court, it has to complete the rulemaking process, which involves hearings and comment periods. The final rule is likely to be issued by the end of 2025 or early 2026, according to Lazarus and Jenks.

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Challenges to the final rule are expected almost immediately.

The first hurdle will likely involve whether opponents possess sufficient legal standing (essentially, a large enough personal stake or connection) to pursue a case. They will need to demonstrate that they have been or will be injured by the government action and winning the suit would address the injury.

With something as amorphous and diffuse as climate change, a skeptical court might have trouble seeing that challengers should have the right to claim standing, Lazarus said.

The court in 2007 held that those challenging the EPA possessed the requisite standing, but the three justices who dissented remain on the court. One of them — Chief Justice Roberts — has long had a particular interest in the standing issue, Lazarus said.

Another potential technical argument is that greenhouse gas emissions don’t qualify as air pollution under the Clean Air Act, because it was enacted to combat traditional particulate and chemical pollution from definite sources, affecting people’s health locally and regionally. So even if they are causing climate change, greenhouse gases can’t be regulated by the Clean Air Act because they’re not the kinds of pollutants the act envisions, the administration is arguing.

In addition, it might be argued that attempting to regulate greenhouse gases is too broad an approach, because it lumps several potential pollutants together when considering their impact on human health and welfare.

Any analysis, the EPA says in its proposed rule, should be performed pollutant by pollutant and be limited to emissions from new motor vehicles — only in the U.S. — that are being regulated.

That type of assessment, Lazarus said, risks atomizing a real, albeit global, problem endangering people’s lives and welfare into fragments that, individually, may not make a strong case for regulation.

Though the consensus view of climate change science is potentially persuasive, it is only after any case clears those legal hurdles that the science would come into consideration, Lazarus said.

The administration is also pursuing a strategy that might tie the hands of future presidents, Jenks said.

Included in the rule is the determination that the interpretation of the current EPA is the best reading of the law. If the Supreme Court agrees, that will hamper future agency officials from tougher regulation without going to Congress to change the Clean Air Act, which Lazarus and Jenks agreed would be unlikely in the near future.

“They are trying to assert, or they’re at least proposing, certain ways of arguing this that would bind a future administration,” Jenks said. “They’re arguing in their primary proposal that this is the best and only reading of the Clean Air Act, which would say a future administration could not do something different.”

Once the EPA finalizes its rule, those challenging its legality would first go to the U.S. Court of Appeals in Washington, D.C., and it would take a year or so to be heard and decided. An appeal to the Supreme Court would be likely later in 2027, with a decision possible in June 2028, just months before the end of the president’s current term.