Another big decision from the Supreme Court today. The Court's conservatives united to overturn a 1984 case which established what is known as Chevron deference. This will be a major blow to the executive branch which can now expect a lot more scrutiny from the courts.

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.”

The ordinary Americans involved in this case were a group of fisherman who had been required to pay for the privilege of having government monitors aboard their boats.

Both cases involved a 1976 federal law that requires herring boats to carry federal observers to collect data used to prevent overfishing. Under a 2020 regulation interpreting the law, owners of the boats were required not only to transport the observers but also to pay $700 a day for their oversight.

Fishermen in New Jersey and Rhode Island sued, saying the 1976 law did not authorize the relevant agency, the National Marine Fisheries Service, to impose the fee.

Two appeals courts — one in Washington, the other in Boston — ruled that the deference called for by the Chevron decision required a ruling for the government. The United States Court of Appeals for the District of Columbia Circuit, in Washington, ruled that the agency’s interpretation of the 1976 law “to allow industry-funded monitoring was reasonable.” The First Circuit, in Boston, said that “at the very least” the agency’s interpretation of the 1976 law was “certainly reasonable.”

Over at Slate an angry Mark Joseph Stern says SCOTUS is "kneecapping the administrative state." There's a more even-keeled discussion over at SCOTUSblog:

Chevron deference, Roberts explained in his opinion for the court on Friday, is inconsistent with the Administrative Procedure Act, a federal law that sets out the procedures that federal agencies must follow as well as instructions for courts to review actions by those agencies. The APA, Roberts noted, directs courts to “decide legal questions by applying their own judgment” and therefore “makes clear that agency interpretations of statutes — like agency interpretations of the Constitution — are not entitled to deference. Under the APA,” Roberts concluded, “it thus remains the responsibility of the court to decide whether the law means what the agency says.”

Roberts rejected any suggestion that agencies, rather than courts, are better suited to determine what ambiguities in a federal law might mean. Even when those ambiguities involve technical or scientific questions that fall within an agency’s area of expertise, Roberts emphasized, “Congress expects courts to handle technical statutory questions” – and courts also have the benefit of briefing from the parties and “friends of the court.”...

Justice Clarence Thomas penned a brief concurring opinion in which he emphasized that the Chevron doctrine was inconsistent not only with the Administrative Procedure Act but also with the Constitution’s division of power among the three branches of government. The Chevron doctrine, he argued, requires judges to give up their constitutional power to exercise their independent judgment, and it allows the executive branch to “exercise powers not given to it.”

Justice Gorsuch also wrote a concurrence which frames this pretty dramatically. I'll quote a bit of his lengthy argument.

In disputes between individuals and the government about the meaning of a federal law, federal courts have traditionally sought to offer independent judgments about “what the law is” without favor to either side.  Marbury v. Madison, 1 Cranch 137, 177 (1803).  Beginning in the mid 1980s, however, this Court experimented with a radically different approach. Applying Chevron deference, judges began deferring to the views of executive agency officials about the meaning of federal statutes.  See Chevron U. S. A. Inc. v. Natural Resources Defense Council, Inc., 467 U. S. 837 (1984).  With time, the error of this approach became widely appreciated. So much so that this Court has refused to apply Chevron deference since 2016.  Today, the Court places a tombstone on Chevron no one can miss...

Whenever we confront an ambiguity in the law, judges do not seek to resolve it impartially according to the best evidence of the law’s original meaning.  Instead, we resort to a far cruder heuristic: “The reasonable bureaucrat always wins.”  And because the reasonable bureaucrat may change his mind year-to-year and election-to-election, the people can never know with certainty what new “interpretations” might be used against them.  This “fluid” approach to statutory interpretation is “as much a trap for the innocent as the ancient laws of Caligula,” which were posted so high up on the walls and in print so small that ordinary people could never be sure what they required...

In all these ways, Chevron’s fiction has led us to a strange place. One where authorities long thought reserved for Article III are transferred to Article II, where the scales of justice are tilted systematically in favor of the most powerful, where legal demands can change with every election even though the laws do not, and where the people are left to guess about their legal rights and responsibilities.  So much tension with so many foundational features of our legal order is surely one more sign that we have “taken a wrong turn along the way.” ...

How bad is the problem?  Take just one example.  Brand X concerned a law regulating broadband internet services. There, the Court upheld an agency rule adopted by the administration of President George W. Bush because it was premised on a “reasonable” interpretation of the statute. Later, President Barack Obama’s administration rescinded the rule and replaced it with another.  Later still, during President Donald J. Trump’s administration, officials replaced that rule with a different one, all before President Joseph R. Biden, Jr.’s administration declared its intention to reverse course for yet a fourth time.  See Safeguarding and Securing the Open Internet, 88 Fed. Reg. 76048 (2023); Brand X, 545 U. S., at 981–982.  Each time, the government claimed its new rule was just as “reasonable” as the last. Rather than promoting reliance by fixing the meaning of the law, Chevron deference engenders constant uncertainty and convulsive change even when the statute at issue itself remains unchanged...

Though our dissenting colleagues have not hesitated to question other precedents in the past, they today manifest what Justice Douglas called an “acute conservatism” for Chevron’s “startling” development, insisting that if this “coveted anchorage” is abandoned the heavens will fall. But the Nation managed to live with busy executive agencies of all sorts long before the Chevron revolution began to take shape in the mid1980s. And all today’s decision means is that, going forward, federal courts will do exactly as this Court has since 2016, exactly as it did before the mid-1980s, and exactly as it had done since the founding: resolve cases and controversies without any systemic bias in the government’s favor.

We'll have to wait and see how significant this change is in the coming years but judging from the reactions on the left over its demise, the change could be quite significant.