The late Supreme Court Justice John Paul Stevens, a Republican appointee who eventually became a liberal voice, famously said that he didn’t move left—the court moved right.

One of his most consequential opinions, Chevron v. Natural Resources Defense Council, shows that as much as anything Stevens touched in his 35 years on the high court.

The 1984 ruling generally gave administrative agencies more leeway to interpret ambiguous federal statutes. It was a 6-0 decision that Stevens thought was merely a common-sense application of previous rulings. It makes “a lot of sense to give the people in the government who have the most specialized knowledge of the particular area a preference that, when in doubt, you go along with their view,” Stevens said in 2018.

But over 35 years, Chevron has come to be known as a foundational ruling that has touched on everything from labor laws to the environment to the economy. Some conservative thinkers now say it created an administrative state of unelected bureaucrats that need to be reined in, and want to see the doctrine scrapped.

Nobody, “including Justice Stevens, thought Chevron was a big deal at the time,” Notre Dame law professor Jeffrey Pojanowski said.

Chevron is truly an example of the court—and politics—shifting around the justice, said former clerk John Flynn, who is now at Stevens’ former firm Jenner & Block.

Befitting Stevens’ humble nature, he meant for Chevron to be a deferential decision, merely a check on unreasonable agency action, Flynn said. While Stevens in 2018 said the decision was “dead right,” he “was by no means its most fervent champion,” said Columbia administrative law professor Thomas Merrill—at least not initially.

Stevens early on argued for a narrower interpretation of Chevron that’s more in line with how Chevron’s critics now apply the doctrine, Pojanowski said. Then the doctrine developed into something more powerful than Stevens originally intended—in part because it was embraced by a conservative icon of the court.

Radical Shift

Just a few years after Chevron was handed down, Stevens and longtime colleague Justice Antonin Scalia disagreed about the doctrine, Pojanowski said.

The dispute wasn’t over whether the ruling was correct. They agreed it was. Instead it related to how broadly it should be applied. Stevens sought a more limited application; Scalia advocated for a more robust one, Merrill said.

So for much of its history, a broad application of Chevron was generally supported by conservatives, Merrill said.

That began to change after the election of President Bill Clinton, said administrative law professor Michael A. Livermore, who teaches at the University of Virginia.

Prior to Clinton’s election, there had been a nearly unbroken chain of Republican presidents, and an even stronger string of Democratically controlled Congresses, Livermore said.

Chevron empowers “administrators at the expense of Congress,” Merrill said.

So it’s no surprise that conservatives like Scalia wanted to expand Chevron, Livermore said.

When the parties in charge changed, conservatives no longer saw Chevron as a way to ensure deference for Republican presidents, but instead as a doctrine that would apply to all administrations—Republican or Democrat, Livermore said.

Calls to overturn Chevron outright increased during the Obama administration, which used executive power robustly, he said. Criticism from the right focused on Chevron allowing regulators to make policies “that should be determined by Congress,” Merrill said.

Overturning Chevron

The confirmation of Trump’s two high court nominees emboldened calls to scrap the doctrine. The prospects for overturning Chevron, however, dampened earlier this year when the court refused to undo a related agency deference doctrine known as Auer deference.

It would be surprising now if the court were to overrule Chevron, Pojanowski said.

“The same arguments against Chevron apply to arguments about Auer deference, and there were not 5 votes to overrule Auer,” he noted. In fact, “there are additional arguments against Auer that do not apply to Chevron,” Pojanowski said.

Stevens said in 2018 that the doctrine of stare decisis—respect for precedent-—alone “certainly should protect a decision that has been repeatedly decided over many, many years, and almost never disagreed with.” He noted that Chevron had been positively cited by lower courts more than 15,000 times.

The fact that the justices are even considering overturning such a longstanding doctrine “reflects on the court itself,” Stevens said.