This week the Supreme Court will hear a case that could hamstring how the federal government regulates everything from water pollution and organic tomatoes to overtime pay and veteran’s benefits.

The case, Kisor v. Wilkie, concerns, on its surface, a Vietnam vet trying to get medical treatment from Veterans Affairs for PTSD, and whether a particular incident in his service is relevant or not to his medical condition.

But what it’s really about is whether courts should defer to agency interpretations of the laws they execute and the regulations they pass to do so.

This seemingly arcane question has enormous practical consequences.

For regulatory agencies to do their jobs, they must interpret thousands of vague congressional demands. What is a “stationary source” of pollution? What, exactly, constitutes “child abuse?” When is an injury “relevant” to a medical claim?

Since 1945—not long after the birth of the modern administrative state—courts have deferred to agencies’ interpretations both of the statutes they enforce, now known as Chevron deference, after a 1984 case, and of their own regulations, known as Auer deference, after a 1997 unanimous decision written by the late Justice Antonin Scalia.

The deference isn’t unlimited—the agency interpretation must still be reasonable, and not clearly erroneous—but courts do not substitute their judgment for that of the agency in charge of administering the law.

Auer deference is on the chopping block this week, as four of the five conservative justices on the Supreme Court have indicated they’d like to see it overturned.

“The doctrine is contrary to the Constitution’s separation of powers,” said Karen Harned, executive director of the National Federation of Independent Business Small Business Legal Center, on a press call sponsored by the right-leaning Federalist Society. “Because the same entity writes the law and then interprets it.”

In principle, there’s some truth to that: first an agency writes a regulation, and then their interpretations of that regulation are respected by courts.

But in practice, that’s not really true. It’s Congress that has delegated this authority to agencies, and Congress can always take it away. Congress can even step in and overturn a specific interpretation, should it choose to do so. Actually, nothing is being done that hasn’t been authorized by, and subject to the review of, Congress.

Conservatives have also argued that Auer deference lets agencies do an end-run around the Administrative Procedure Act: they can issue vague regulations in the public process, and then “interpret” those regulations on their own.

Trouble is, that doesn’t happen much either. An exhaustive study by two law professors yielded no evidence that agencies more often wrote vague regulations after Auer than before. In the words of one of them, Adrian Vermeule, “Let us pause to absorb this: Much of the clamor against Auer has been premised on an empirical claim about agency behavior now shown to lack any discernible factual basis.”

So what’s really going on?

“This case has to be understood against the background of conservatives’ attack on the administrative state,” said Columbia Law School professor Gillian Metzger. “The attack on Auer deference is to make it harder for agencies to develop coherent, well-functioning regulatory regimes.”

No surprise, then, that briefs in support of overturning Auer have been filed by an array of right-wing groups from the National Right-to-Work Legal Defense Foundation (which tends not to like Labor Department regulations) to the Chamber of Commerce (which would prefer fewer regulations in general) and many others. While on the other side are the AFL-CIO, environmental groups, and other public interest nonprofits.

“ If Chevron and Auer are axed, every decision that every agency makes would be subject to fresh review by the courts. ”

And no surprise that the solicitor general, who is supposed to defend the VA’s decision, has instead told the Court to severely limit Auer and defer to agency interpretations only if a host of demands are met.

And finally, no surprise that the fate of Kisor is dependent less on the principles involved than on counting the conservatives (five) now on the Supreme Court. After all, “rolling back the administrative state” has long been one of the primary goals of the Republican presidents who appointed those conservatives.

Moreover, it’s clear that it’s not just Auer that’s in the sights of conservatives; it’s Chevron as well. “I think the separation of powers argument holds up for both,” Harned told The Daily Beast. “I would argue with Chevron too. It takes judges out of judging and puts the thumb on the scale in favor of administrative agencies.”

Of course, it’s really Congress that put its thumb on the scale. Congress has neither the time nor the expertise to specify every possible detail of every regulation. For example, Chevron itself was about the highly specialized question of whether a single industrial facility with multiple smokestacks counted as a single source of pollution or multiple sources of pollution. So Congress left it to the EPA, with its expertise, to decide such matters.

But if Chevron and Auer are axed, every decision that every agency makes would be subject to fresh review by the courts, who, of course, have no expertise whatsoever in smokestacks or post-traumatic stress diagnoses. The result would be massive regulatory uncertainty, and an explosion in litigation, both of which would severely hamper agencies’ ability to regulate pollution, labor conditions, food safety, or anything else for that matter.

The very structure of administrative agencies themselves—agencies like the Securities and Exchange Commission, for example—which often combine quasi-judicial and administrative functions, would be called into question.

Which, surely, is the point. Of course, Auer deference isn’t exactly headline news. But it’s a key brick in the wall of the modern state—the same modern state that oligarch-funded libertarian and conservative think tanks are seeking to deconstruct. Take out this brick, followed by the larger bricks of Chevron and others, and the entire edifice begins to fall apart.

Leaving the hugely powerful entities that these agencies were meant to counterbalance to do whatever they want.