The U.S. Supreme Court struck down a precedent Friday that had for decades limited judicial power to strike executive branch regulations, in a decision immediately criticized for potentially undermining decisions by scientists and agency experts.

The 6-3 and 6-2 decisions in two cases brought by fishing operators in New Jersey and Rhode Island challenged a National Oceanic and Atmospheric Administration rule and overturned the principle known as Chevron deference.

That precedent gave federal agencies broad discretion to use their judgment to resolve any ambiguity Congress left in a federal statute.

The court’s six conservatives reasoned that courts “routinely confront statutory ambiguities” that have nothing to do with the authority of regulatory agencies, Chief Justice John Roberts wrote in the majority opinion.

“Of course, when faced with a statutory ambiguity in such a case, the ambiguity is not a delegation to anybody, and a court is not somehow relieved of its obligation to independently interpret the statute,” Roberts wrote.

Under the 40-year-old precedent, courts gave up their interpretive role and deferred to agencies, Roberts wrote.

But they shouldn’t, he added. Judges should apply their own legal reasoning to reach a sound decision.

“Courts instead understand that such statutes, no matter how impenetrable, do —? in fact, must — have a single, best meaning.”

1984 ruling overturned

The decision overturned Chevron v. Natural Resources Defense Council, a 1984 Supreme Court ruling that said courts must defer to federal agencies’ expertise when considering legal challenges to a rule. The 1984 ruling significantly raised the bar for overturning an agency rule.

The precedent strengthened the executive branch under presidential administrations of both parties, but experts worry its reversal will strip agencies of the power to enact regulatory safeguards across a broad spectrum of issues including clean air and public health.

In a dissenting opinion, the court’s three liberals — not including Justice Ketanji Brown Jackson in one of the cases, after she recused herself because she’d heard the case as an appeals court judge before joining the Supreme Court — said the majority erred by misunderstanding the roles of three branches of government.

Congress knows it cannot “write perfectly complete regulatory statutes,” Justice Elena Kagan wrote in a dissent. Interpretation of those statutes is a given, and Congress usually prefers a “responsible agency” instead of a court.

Agencies are more politically accountable and have greater technical expertise in a given issue than courts, she wrote.

“Put all that together and deference to the agency is the almost obvious choice,” Kagan wrote.

Kagan went on to criticize the decision as a power grab by the judiciary at the expense of agency experts.

“A rule of judicial humility gives way to a rule of judicial hubris,” she wrote. “In one fell swoop, the majority today gives itself exclusive power over every open issue—no matter how expertise-driven or policy-laden—involving the meaning of regulatory law.”

Liberals see a weakening of safeguards

Liberal groups and elected Democrats worried the reversal will strip agencies of the power to enact strong regulatory safeguards across a broad spectrum of issues, especially climate and environmental regulations.

“It weakens our government’s ability to protect us from the climate crisis, threats to worker safety, public health, clean air and water, safe medicines and food, a sound financial system, and more,” Manish Bapna, president of the environmental group NRDC Action Fund, wrote in a statement.

“Today’s reckless but unsurprising decision from this far-right court is a triumph for corporate polluters that seek to dismantle common-sense regulations protecting clean air, clean water and a livable climate future,” Wenonah Hauter, the executive director of the advocacy group Food & Water Watch, said in a statement.

Rachel Weintraub, the executive director of the Coalition for Sensible Safeguards, a group that advocates for strong federal regulations, said in an interview before the decision was released that Chevron deference has allowed a host of regulations affecting consumer safety, labor, environmental protections and other issues.

“The important role that government plays in ensuring the health and safety of our families and the fairness of our markets could be undermined here,” she said.

The ruling takes power away from the experts on a particular subject of a federal regulation — traffic engineers at the Department of Transportation, disease experts at the Food and Drug Administration or scientists at the Environmental Protection Agency, for example — and gives it to the federal judiciary, Weintraub said.

U.S. Rep. Raúl Grijalva, an Arizona Democrat who is the ranking member on the U.S. House Natural Resources Committee, called the ruling a gift to polluters and the fossil fuel industry.

“For 40 years, Congress has passed laws with the understanding that the interpretation of those laws is for the courts, but the implementation laid in the hands of the scientific and policy career experts at our federal agencies,” Grijalva said in a statement.

“But now, thanks to this extremist power-grab, our most fundamental protections will be at the whim of individual judges — many of whom are far-right ideologues — regardless of their lack of expertise or political agenda.”

Conservatives applaud rollback

Republicans in Congress and conservative activists praised the decision for weakening the administrative state, saying it would return power to the legislative branch.

“The Constitution vests Congress with the sole authority to make law,” Senate Republican Leader Mitch McConnell of Kentucky said in a statement. “After forty years of Chevron deference, the Supreme Court made it clear today that our system of government leaves no room for an unelected bureaucracy to co-opt this authority for itself.”

Rep. Bruce Westerman, an Arkansas Republican who chairs the House Natural Resources Committee, said Friday’s ruling should spur Congress to write more prescriptive laws.

“Congress has sidestepped our legal duties for far too long and today’s ruling puts us back in the driver’s seat when it comes to rulemaking and regulatory authority,” Westerman said in a written statement. “We’re no longer going to let federal agencies fill in the details when it comes to the policies we enact.”

Roman Martinez, an attorney who argued on behalf of the Rhode Island fishing operators, called the ruling a “win for individual liberty and the Constitution.”

“The Court has taken a major step to shut down unlawful power grabs by federal agencies and to preserve the separation of powers,” Martinez said in a statement distributed by the conservative public relations firm CRC Advisors. “Going forward, judges will be charged with interpreting the law faithfully, impartially, and independently, without deference to the government.”

No plans to reopen old cases

In the majority opinion, Roberts said the court did not plan to reopen cases that had been decided by Chevron “despite our change in interpretive methodology.”

Even prior to Friday’s decision, the court had used Chevron less often. During the oral argument, Roberts cited a study that the court had relied on the precedent sparingly over the past 14 years.

The court’s conservative majority has shown a willingness to move away from deference to agency decision-making, demanding more explicit congressional instruction.

In West Virginia v. EPA in 2022, for example, the court ruled that the EPA lacked the authority under the Clean Air Act to regulate greenhouse gas emissions.

Daniel Wolff, an administrative law attorney at the law firm Crowell & Moring, downplayed the effect the ruling would have on the administrative state.

Congress at times explicitly directs agencies to craft regulations, and those rules will still be subject to the same standard that they were written reasonably, Wolff said in an interview prior to the decision.

Rules with solid legal and statutory foundations would survive under either standard, he said.

“Rolling back Chevron is simply going to mean agencies don’t get the benefit of the doubt in the case of a tie,” Wolff said. “They have to come into the court and persuade the court that they have the better reading of the statute.”

Fishing operators

The cases decided Friday was brought by herring fishing operators from New Jersey and Rhode Island who challenged a NOAA rule requiring the operators to pay for the federal monitors who regularly join fishing boats to ensure compliance with federal regulations.

The fishing operators said the rule forced them to hand over up to 20% of their profits.

After a lower court relied on Chevron deference to rule in favor of NOAA, oral arguments at the Supreme Court in January focused almost entirely on Chevron.