On Monday, Justice Brett Kavanaugh sent the clearest signal yet that the Supreme Court’s conservative majority is ready to take a wrecking ball to federal regulations. By doing so, the court could jeopardize a vast swath of laws that govern pollution, Wall Street, wage and hour rules, campaign finance limits, and more.

Kavanaugh’s fellow conservative justices already declared their disdain for the “administrative state”—that is, the agencies that interpret and enforce federal law—in June’s Gundy v. United States. All four conservatives argued for a revival of the “nondelegation doctrine,” which bars Congress from transferring its legislative power to another branch of government. But Kavanaugh did not join the court in time to hear Gundy. As a result, Justice Elena Kagan and her fellow liberals were able to stave off an assault on the federal bureaucracy. The big question, then, was whether Kavanaugh would join the conservatives’ crusade.

On Monday, Kavanaugh announced that he is, indeed, on board. In a short opinion, Kavanaugh wrote that the Constitution may bar Congress from directing federal agencies to “to decide major policy questions.” This issue, he noted, “may warrant further consideration in future cases.” Since most federal agencies are located within the executive branch, the doctrine would bar lawmakers from authorizing these agencies to make “policy decisions.” Instead, as Kavanaugh put it, agencies could only “decide less-major or fill-up-the-details decisions.”

The list of statutes susceptible to attack under a revived nondelegation doctrine is lengthy.

What, you might ask, distinguished “major” and “less-major” policy decisions? No one really knows. That’s a key reason why the Supreme Court has only invoked the nondelegation doctrine to strike down a law twice in history—both times in 1935, at the height of the judicial revolt against the New Deal. Ever since, SCOTUS has only asked whether Congress gave agencies an “intelligible principle” to follow. If so, it upheld the law.

There is good reason for this deference. Agencies are not democratically unaccountable, as their critics often claim. They are run by commissioners who serve a fixed term. The president nominates these commissioners and the Senate must confirm them; if citizens dislike their decisions, they can vote out the lawmakers who put them in charge. New rules must typically be proposed to the public, which may then provide input that the agency has to consider. Congress can overturn these rules at any time.

More importantly, the Constitution contains no nondelegation clause; it merely vests all “legislative Powers” in Congress. When lawmakers instruct an agency to address some problem—say, air pollution—it is employing those constitutional powers, with the recognition that it lacks the expertise to address each pollutant under ever-changing circumstances. Or, as University of Michigan law professor Nicholas Bagley put it: “Congress does not surrender its legislative power by delegating. It exercises that power.”

Kavanaugh seemed to reject that view of nondelegation, suggesting instead that Congress can’t delegate “major policy questions” to agencies. If and when the Supreme Court enshrines this view into law, a slew of vital laws will be on the chopping block. Most vulnerable are environmental laws, which give the Environmental Protection Agency wide latitude to curb pollution. For instance, the Clean Air Act compels power plants to reduce emissions to the level of “the best system of emission reduction.” The EPA decides that standard. Federal laws also direct the agency to regulate numerous other pollutants and toxins, including carbon, mercury, and lead. Does Congress’ delegation of this duty give the EPA impermissible control over a “major policy question?” Again, that’s in the eye of the beholder, but there’s good reason to think that SCOTUS’s conservative majority would say yes.

The list of statutes susceptible to attack under a revived nondelegation doctrine is lengthy. Campaign finance laws that entrust the Federal Election Commission to limit coordination between political campaigns and outside groups? Likely gone. (Such coordination allows candidates to easily skirt campaign finance limits.) Workplace laws that charge the Department of Labor with adjusting wage, hour, and overtime rules? Possibly doomed, as well. Laws regulating drugs, tobacco, firearms, crime, and immigration are shot through with significant delegations to federal agencies. Those may soon be on the chopping block.

Worse, the nondelegation doctrine may be applied in a manner that’s inconsistent—and politically charged—because the standard is so subjective: A “major policy question” is whatever five justices say it is, and there may be overlap between what those justices say and what the Republican Party desires.

Defenders of the nondelegation doctrine like Neil Gorsuch and Kavanaugh insist that their theory would restore legislative power to Congress. That is misleading at best. The doctrine would limit Congress’ power to delegate authority to agencies, giving courts a new veto over the people’s representatives. It is a theory that aggrandizes the dominance of courts over Congress, not Congress over agencies. And it is resurgent just as Republicans gain control over the judiciary. Kavanaugh’s opinion on Monday gives enemies of federal regulation—over the environment, the economy, our elections, you name it—a gift that could keep giving for decades to come.