This article by Grist is published here as part of the global journalism collaboration Covering Climate Now.

The Supreme Court on Friday threw into question the future of climate and environmental regulation in the United States, scrapping a decades-old legal precedent that gave federal agencies leeway to interpret laws according to their expertise and scientific evidence. The impact of the decision to scrap the so-called Chevron deference will take years to become clear, but it could allow for far more legal challenges against regulations by agencies like the EPA and the Department of the Interior that have a huge role in the climate fight. 

Federal courts have long deferred to federal agencies to interpret laws that are unclear and need further clarification. In 1984, a shorthanded Supreme Court ruled in a unanimous decision that federal agencies have the final say on ambiguous policies, which allowed those agencies broad authority to make decisions without fear of judicial override. 

In Supreme Court filings, the Biden administration said that overruling the Chevron deference would be a “convulsive shock to the legal system.”

Environmental organizations also condemned the decision. 

“Today’s ruling sidelines the role of agency expertise, and instead shifts power to judges who do not have the expertise of agency staff who live and breathe the science, financial principles, and safety concerns that federal agencies specialize in,” Kym Meyer, the litigation director for the Southern Environmental Law Center, said in a statement. 

Vickie Patton, general counsel for the Environmental Defense Fund, said the decision “undermines vital protections for the American people at the behest of powerful polluters.”

Writing for a 6-3 majority, Chief Justice John Roberts argued that “courts must exercise their independent judgment in deciding whether an agency has acted within its statutory authority.” He called the Chevron decision a “fundamental disruption of our separation of powers,” one that “improperly strips courts of judicial power by simultaneously increasing the power of executive agencies.”

The current conservative Supreme Court no longer relies much on Chevron to decide big cases involving the executive branch; Roberts noted during the oral arguments for the Loper Bright Enterprises v. Raimondo case, also on the docket this session, that the court has gone “14 or 16” years since issuing a decision citing the Chevron precedent. Instead, the court in several recent decisions has outlined its own standard for evaluating regulations. This standard, which the court’s conservative justices call the “major questions doctrine,” prohibits agencies from making rules on issues of “economic and political magnitude” without clear directives from Congress. The court has never outlined what constitutes an issue of such magnitude, but it cited the “major questions” test in a landmark 2022 case that limited the EPA’s authority to regulate greenhouse gases.

Lower courts, however, still cite the Chevron deference in many cases, and federal agencies win most of them: An analysis of more than 1,500 circuit court decisions between 2003 and 2013 found that courts applied Chevron in 77 percent of regulatory disputes, and that agencies won many more of cases than they did cases where courts did not use Chevron. The Department of the Interior, which handles many issues related to climate change, oil leasing, endangered species, and Indigenous affairs, was one of the agencies that relied on Chevron the most. 

The Biden administration and numerous legal scholars had urged the court to keep the precedent in place, arguing that overturning it would create regulatory chaos as hundreds of plaintiffs sued to challenge past rules. In his decision, Roberts rebuffed the idea that the court’s move to throw out Chevron would cause a deluge of lawsuits against past regulation, saying the decision shouldn’t call into question the numerous past cases that relied on the precedent. 

“The holdings of those cases that specific agency actions are lawful—including the Clean Air Act holding of Chevron itself—are still subject to statutory stare decisis despite our change in interpretive methodology,” he wrote, referring to a legal principle that argues judges should leave intact most past decisions.

In her dissent, Justice Elena Kagan expressed skepticism of that claim, saying she found the majority too “sanguine” about the impact of tossing Chevron, arguing the precedent helped keep “air and water clean, food and drugs safe, and financial markets honest.” She accused the conservative bloc of trying to turn the Supreme Court “into the country’s administrative czar.” 

“What’s at stake [in the decision] is whether courts are going to defer to agencies interpreting statutes,” said Michael Burger, the director of the Sabin Center for Climate Change Law at Columbia University, “or whether courts are going to stop doing that, and with more regularity take it on themselves to interpret the statutes even when they’re ambiguous, which means they may be in the position of making more policy choices.” 

The main case in question this year, Loper Bright, concerned a National Marine Fisheries Service regulation that requires herring fishers to pay for monitors on their boats. The underlying law in question provides for monitors to ride on boats and make sure fishermen aren’t overfishing, but it doesn’t say whether the government can require fishing boat companies to pay for them. A commercial fishing company represented by lawyers who have ties to conservative energy billionaire Charles Koch’s political organization is suing to overturn the monitor rule—and also asking the court to throw out the Chevron standard altogether.

The original Chevron decision upheld an attempt to weaken environmental regulations, rather than strengthen them. The Environmental Protection Agency under Ronald Reagan sought to loosen the standard for calculating air pollution emissions from industrial facilities, and the Natural Resources Defense Council, or NRDC, sued to argue that the EPA didn’t have the authority to offer a new interpretation of the Clean Air Act. NRDC won at first, but Chevron appealed the decision to the Supreme Court, which sided with Reagan’s EPA.

But over the past decade, many conservatives have come to believe that the precedent allows the executive branch to overreach its authority, and overturning it has become a rallying cry for many right-wing activists and legal scholars.

“There’s a feeling that Chevron favors regulation,” said Burger. “And if you take away the deference and you give power to courts, then the increasing number of conservative judges in the federal court system have more authority, and that’s going to have the effect of chilling agencies.”