The Supreme Court on Friday significantly weakened the power of federal agencies to approve regulations in a major decision that could have sweeping implications for the environment, public health and the workplace.

The 6-3 ruling, overturning a precedent from 1984, will shift the balance of power between the executive and judicial branches and hands an important victory to conservatives who have sought for years to rein in the regulatory authority of the “administrative state.”

The lawsuits were filed by two groups of herring fishermen challenging a Commerce Department regulation requiring them to pay the salaries of government observers who board their vessels to monitor the catch. But the decision will net a far wider swath of federal regulations affecting many facets of American life.

The decision overturns the Chevron v. Natural Resources Defense Council precedent that required courts to give deference to federal agencies when creating regulations based on an ambiguous law. Congress routinely enacts open-ended laws that give latitude to agencies to work out — and adjust — the details to new circumstances.

“Chevron is overruled,” Chief Justice John Roberts wrote in his majority opinion. “Courts must exercise their independent judgment in deciding whether an agency has acted within its statutory authority.”

Justice Neil Gorsuch, the son of a former Environmental Protection Agency administrator, wrote separately to call Chevron Deference “a grave anomaly when viewed against the sweep of historic judicial practice.”

The 1984 decision, he said, “undermines core rule-of-law values ranging from the promise of fair notice to the promise of a fair hearing,” adding that it “operated to undermine rather than advance reliance interests, often to the detriment of ordinary Americans.”

Liberals say ruling is ‘judicial hubris’

Justice Elana Kagan, writing a dissent joined by the court’s two other liberals said that, with the overturning of Chevron, “a rule of judicial humility gives way to a rule of judicial hubris.”

“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. As if it did not have enough on its plate, the majority turns itself into the country’s administrative czar,” Kagan wrote.

The majority, she added, “disdains restraint, and grasps for power.”

Conservatives have long sought to rein in regulatory authority, arguing that Washington has too much control over American industry and individual lives. The justices have been incrementally diminishing federal power for years, but the new case gave the court an opportunity to take a much broader stride.

In the case of the fishermen who brought the case, the law allowed the government to mandate the observers but was silent on the question of who had to pay their salaries, which the fisherman argue added roughly $700 a day to their costs. They encouraged the court to rule that agencies couldn’t enact such a requirement without explicit approval from Congress.

The Supreme Court had been trending in that direction for years, knocking back attempts by federal agencies in other contexts to approve regulations on their own. In 2021, for instance, the court’s conservatives struck down a Biden administration effort to extend an eviction moratorium first approved during the Trump administration. Last year, the court’s conservatives similarly invalidated a Biden plan to wipe out student loans of millions of Americans.

This story has been updated with additional details.