After a bizarre (and long) set of Supreme Court arguments on two of the recent federal vaccine mandates, the most likely outcome is that the rule affecting private businesses will be blocked while that affecting healthcare providers receiving federal funds will be allowed to go into effect pending further litigation. That is, there seem to be six votes to stay the private-sector mandate because it goes beyond the power Congress gave OSHA (without reaching the issue of Congress can properly grant that power), while a majority either seem comfortable with the healthcare-worker mandate or might think the states (as opposed to the providers) don’t have standing to challenge it.

But to be clear: these cases present different sorts of questions, the first about the scope of federal power and the second about the conditions Congress can attach to Medicare/​Medicaid funds (and so technically shouldn’t even be called a “mandate”).

The OSHA rule affects far more people and represents a novel use of federal regulatory authority, so there’s understandably more attention on that litigation. But after more than two hours of argument in those consolidated cases, it’s clear that the justices can’t even agree on what the legal issues are. Justice Sonia Sotomayor, setting aside her various factual errors, seems to think that there’s a federal “police power,” at least so long as OSHA is constitutional. Justice Neil Gorsuch, in contrast, was dubious of claims of sweeping administrative authority in a novel circumstance based on vague (or what Justice Brett Kavanaugh called “cryptic”) statutory language.

Justice Kagan would defer to experts, while Chief Justice John Roberts was skeptical of a federal attempt to “work around” legal limits regardless of who was making the judgment calls. Justice Amy Coney Barrett, widely considered to be the deciding vote, expressed concern that the mandate was written too broadly—for example, covering some outdoor workers but not all indoor workers—and didn’t follow normal procedures. (And indeed, OSHA’s “emergency” standards tend to fail in court more often than not.)

One interesting development was the significant discussion of the “major question doctrine” (sometimes known as the “major rule doctrine”) which holds that Congress must speak clearly when giving significant authority to administrative agencies. As Justice Antonin Scalia put it 20 years ago, Congress doesn’t “hide elephants in mouseholes.” Here that means that, much as the Court found in blocking the CDC’s eviction moratorium, a minor or ancillary statutory provision shouldn’t be read to delegate the awesome power of imposing vaccines on more than 100 million Americans, significantly disrupting our economy.

Several justices invoked the major questions doctrine—and perhaps they’ll also be thinking of another doctrine of the same name, which suggests that rather than deferring to agency interpretations when significant regulations are at issue, courts must determine the correct reading for themselves. This is what Chief Justice Roberts infamously did in King v. Burwell, finding that an Obamacare “exchange established by the state” included federal exchanges — but not because of deference to the IRS on that point.

In any event, the federal government may have some power to impose vaccine mandates, in some circumstances—such as on its own workers, and so long as there are religious and medical exemptions—but the devil is in the details and it can’t do so in an arbitrary or unreasoned manner. Given that no federal agency can impose a general vaccination mandate, precisely because the federal government is one of enumerated powers and lacks a general police power to regulate for the public health and safety (like states have), it’s unconstitutional for OSHA to attempt a “work around” even if Congress purported to give it authority to do so.