During its last session, the Supreme Court’s conservative majority dealt blow after blow to federal agencies’ authority to draft and enforce policies, including those aimed at mitigating climate change. Its decisions have already created upheaval for courts considering issues ranging from the approval of a solar project to vehicle emissions rules. This has upended the legal landscape for judges and for regulators, and could slow climate progress as a result.

The uncertainty has alarmed, but not surprised, legal experts who earlier this summer predicted that four rulings limiting federal authority could curtail the ability of the Environmental Protection Agency and other agencies to limit pollution, govern toxic substances, and mitigate global warming. 

“It’s going to throw climate policy into many years of litigating what these cases actually mean when applied to individual rulemakings,” said Deborah Sivas, an environmental law professor at Stanford University. “That’s not good for the energy transition that we actually need to go through.”

In its most consequential ruling, the Supreme Court overturned the so-called Chevron doctrine, which has since 1984 granted federal regulators broad leeway to use their expertise to interpret ambiguities in the law. Another ruling effectively eliminated a six-year statute of limitations on lawsuits against federal regulations, opening the door to challenges against any policy regardless of how old it is. A lawsuit against the Securities and Exchange Commission invalidated the use of in-house administrative law judges, jeopardizing a key enforcement mechanism used by more than a dozen agencies. And the conservative majority, ruling in Ohio v. EPA, blocked a federal smog reduction plan, a victory for polluters and conservatives who have long argued that EPA regulations create undue burdens. 

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The flurry of litigation stemming from those decisions started with the Supreme Court. On July 2, shortly after discarding Chevron, the court, in a case challenging the Federal Energy Regulatory Commission’s approval of a solar energy project, sent the matter back to the U.S. Court of Appeals for the District of Columbia Circuit. Justices asked the lower court to reconsider it “in light of Loper Bright Enterprises v. Raimondo,” the decision overturning Chevron deference.

That could be an issue, because the D.C. Circuit cited Chevron when it ruled in favor of FERC in February. Utilities had challenged the agency’s decision to make a solar and battery storage facility in Montana eligible for benefits under a 1978 law that requires utilities to purchase power from small renewable energy projects. Utility groups argued that the project in question shouldn’t qualify because its combined power capacity exceeded the size allowed under that law. The D.C. Circuit, invoking Chevron, deferred to the agency in upholding its decision.

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Sivas said the judges most likely will stand by their decision, but will have to explain their reasoning without relying on Chevron. Although this case ultimately could demonstrate the limits of Chevron in turning back regulatory actions — jurists, after all, have other precedents they can cite, including the Skidmore deference that favors agencies when they provide persuasive reasoning for their actions — it is indicative of the litigation to come now that the Supreme Court has “watered down the influence of agencies,” she said. “We’re already in the thick of it.” 

Appellate judges, taking cues from the Supreme Court, have started returning cases to lower courts for reconsideration in light of the high court’s latest rulings. Last month, the 5th Circuit asked a Texas district court to revisit its decision upholding a Department of Labor rule allowing retirement fund managers to consider climate risks when making investments. Republican state attorneys general and fossil fuel companies considered the rule “arbitrary and capricious,” but the Texas court cited Chevron when rejecting their challenge in September. A reversal could imperil the ability of investors to align financial decisions with climate action

In other cases, courts are asking litigants to explain how recent Supreme Court decisions could impact their claims. On July 30, for example, the D.C. Circuit Court asked the plaintiffs in lawsuits challenging vehicle emissions standards established by the EPA and the National Highway Traffic Safety Administration to explain how the Chevron ruling and Ohio v. EPA change their arguments. The rules represented a broader push by the Biden administration to cut emissions from the transportation sector, and could serve as an early test of how such climate policies might fare in a post-Chevron world. 

It would be difficult to overstate the impact the fall of Chevron could have. Although the Supreme Court hasn’t relied on the doctrine for the last dozen or so years, lower courts have leaned on it roughly 17,000 times since 1984 to consider the legality of regulations governing everything from food safety to air pollution. They no longer have that long-standing precedent to guide them.

Jason Rylander, legal director of the Center for Biological Diversity, said the impact of the Supreme Court’s four recent decisions on these cases remains unclear, largely because the end of Chevron by design gives courts greater discretion to rule on agency interpretations of federal law. Until now, he said, Chevron deference “put a small thumb on the scale” in favor of agencies like the EPA. Now, courts must “come up with what they believe to be the best reading of the statute.” They might agree with an agency, they might not. Either way, courts hold more power to reach their own conclusions, sowing greater uncertainty — especially among courts that lean conservative, such as the 5th and 11th circuits.

Sending cases back to lower courts for further review will almost certainly delay decisions, limiting the effectiveness of federal policies to address climate change and other issues. But an even greater impact may be felt by the agencies charged with taking those actions and already facing increasing scrutiny and lawsuits. 

“Agencies will have to be even more careful than they already are to ground proposed regulations in the text of the statute and to explain why they believe that the regulation is consistent with Congressional intent,” Rylander said. 

More concerning, that ongoing legal chaos could discourage agencies from pursuing the bold policies needed to address the climate crisis, Sivas said. 

“If the agencies don’t think they can ever get these things past the judicial review,” she said, “they’re just not going to try to do it.” 

The elimination of Chevron is already a point of contention in debates over FERC’s Order 1920, a rule released three months ago that requires regions to engage in long-term transmission planning to facilitate the deployment of renewable energy. The rule has already faced legal challenges by groups like the Louisiana and Mississippi public service commissions, and opponents have cited the demise of Chevron as one reason jurists should deem the rule invalid. In another jarring example, lawyers for the U.S. Air Force recently told the EPA that the end of Chevron means the Air Force should not be required to heed an order to clean up PFAS-contaminated drinking water at Tucson International Airport in Arizona.

Meanwhile, the fossil fuel industry and other polluters, emboldened by the Supreme Court’s recent decisions, have ramped up challenges to environmental regulations. In late July, Republican state attorneys general, rural electric cooperatives, and fossil fuel trade organizations asked the Supreme Court to pause an EPA rule to reduce the greenhouse gas emissions of coal- and gas-fired power plants. As in Ohio v. EPA, the plaintiffs are once again asking the high court to block the rule even as it wends through the D.C. Circuit. (The Supreme Court previously paused another EPA power plant emissions rule in 2016, the Obama-era Clean Power Plan, which never went into effect.) Legal experts say the outcome of Ohio v. EPA proves the Supreme Court is willing to take such far-reaching actions — and that it has clearly encouraged this request for an emergency pause.

“Industry lawyers believe it is open season to go after regulations,” Michael Gerrard, an environmental law professor at Columbia University, said. Corporate clients, egged on by Ohio v. EPA and other Supreme Court wins, have concluded that “the expense of the lawsuit is small compared to the benefit if they win,” he said.

That attitude is clear from recent publications by major law firms encouraging clients to challenge federal regulations. “Now is a great time to reassess whether to challenge existing rules or prior statutory interpretations,” one major law firm recommended following recent Supreme Court decisions. Akin Gump, a global firm that from 2019 to 2023 earned $7.9 million in fossil-fuel related lobbying, highlighted how the decision in Corner Post, which effectively ended the statute of limitations on challenges to government regulations, creates new opportunities for clients and recommended companies file their lawsuits “in forums that are home to more conservative-leaning judges.”

The expected rise in challenges to environmental regulations is exacerbated by continued gridlock in Congress, Rylander said. Lawmakers are unlikely to revise laws to include detailed language outlining how agencies can act on climate change. That means federal agencies will need to increasingly lean on laws like the Clean Air Act — but they can’t if they’re thwarted by turmoil in the courts. 

“We are at a critical point for climate action, and in the absence of Congressional legislation, we’re going to be asking our federal agencies to do more and more with the statutory tools that they already have,” Rylander said. “If courts start standing in the way of that, then it’s going to be disastrous for meeting our climate goals and for humanity writ large.”