In a 6-3 vote, judges overruled the landmark 1984 ruling in Chevron v Natural Resources Defense Council, which said judges should defer to government agencies in determining a "reasonable" interpretation of the law if the language is ambiguous
In a 6-3 vote, judges overruled the landmark 1984 ruling in Chevron v Natural Resources Defense Council, which said judges should defer to government agencies in determining a "reasonable" interpretation of the law if the language is ambiguous AFP

The conservative-majority US Supreme Court struck down 40 years of legal precedent Friday, curbing the power of federal agencies to regulate critical issues affecting Americans' daily lives, from air quality to drug safety and more.

In a 6-3 vote, judges overruled the landmark 1984 ruling in Chevron v Natural Resources Defense Council, which said judges should defer to government experts in determining a "reasonable" interpretation of the law if the language is ambiguous.

But that had proved to be "fundamentally misguided," and defied the command of a statute asking courts to exercise their independent judgment on whether federal agencies have overreached, said the majority opinion written by Chief Justice John Roberts.

"Courts may not defer to an agency interpretation of the law simply because a statute is ambiguous," Roberts wrote.

The decision divided the court along its conservative-liberal fault line, with the three judges appointed by Democrats -- Elena Kagan, Sonia Sotomayor, and Ketanji Brown Jackson -- voting against.

In a scathing dissent, Kagan criticized what she said was an unwarranted expansion of judicial power.

"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," she said.

"As if it did not have enough on its plate, the majority turns itself into the country's administrative czar."

When the Supreme Court issued its original Chevron decision, it was a win for the administration of Republican president Ronald Reagan, who accused the country's progressive federal judges of burying corporate America under masses of unnecessary and restrictive red tape.

But the political right has since decried the ruling, saying it unfairly empowers the central government over the judiciary and means agencies can alter the meaning of statutes, depending on who is in charge.

The case to the Supreme Court came by way of two challenges to a rule issued by the National Marine Fisheries Service.

Herring companies represented by conservative legal groups with ties to petrochemicals billionaire Charles Koch had complained they were being effectively forced to pay for the federal observers who are monitoring their operations to prevent overfishing.

"Congress expects courts to handle technical statutory questions, and courts did so without issue in agency cases before Chevron," wrote Roberts, though he said the ruling "does not call into question prior cases that relied on the Chevron framework."

But Kagan warned it was the latest in a string of recent decisions by the court that will "cause a massive shock to the legal system."

"It has become part of the warp and woof of modern government, supporting regulatory efforts of all kinds--to name a few, keeping air and water clean, food and drugs safe, and financial markets honest."

Backlash was swift among lawmakers and nonprofits.

Environmental group Earthjustice said the ruling "has granted their request carving out a path for multiple industries to take advantage of the changed landscape to challenge regulations they don't like before judges who will be empowered and emboldened to second-guess federal agencies."

"In overruling Chevron, the Trump MAGA Supreme Court has once again sided with powerful special interests and giant corporations against the middle class and American families," added Democratic Senate Majority Leader Chuck Schumer.

On the other side of the aisle, Republican Speaker of the House Mike Johnson, House Majority Leader Scalise and Whip Tom Emmer hailed the ruling as a "landmark decision" that marks "the beginning of the end of the administrative state."

The Supreme Court has been chipping away at the power of federal agencies in recent years, a trend viewed by observers as part of a wider conservative push, dubbed the "war on the administrative state."

On Thursday, the court ruled the tribunal system used by the Securities and Exchange Commission, Wall Street's government watchdog and rule enforcer, was unconstitutional -- in a major victory for pro-business conservatives.