Justice Barrett’s majority opinion in Trump v. CASA, Inc. assured everyone that vacatur was not on the chopping block: “Nothing we say today resolves the distinct question whether the Administrative Procedure Act authorizes federal courts to vacate federal agency action.” By my lights, CASA did resolve that question—just not in so many words, and not in the way that one would expect. Properly understood, CASA forbids vacatur sometimes but not always. If vacatur is necessary to afford complete relief to an injured plaintiff—say, an unregulated third party—a federal court may vacate the injurious agency action. Otherwise, traditional principles of equity contemplate party-specific relief.

The APA authorizes the reviewing court to “set aside” unlawful agency action. For decades, federal courts (especially the D.C. Circuit) have assumed that “set aside” means “vacate.” Defending this practice in Corner Post, Justice Kavanaugh points out that vacatur is often the only way for unregulated parties to obtain meaningful relief. In the other direction, Justice Gorsuch forcefully argues that the “set aside” phrase must be understood in light of background principles of equity, which do not allow courts to dish out universal relief on behalf of nonparties. Both sides are right. The complete-relief principle splits the difference.

The fact that a party is not the direct object of the challenged regulation does not mean that she is not injured or that a favorable judgment cannot remediate those injuries. Just last Term, the Supreme Court explained that causation and redressability are satisfied if “commonsense economic principles” suggest that a regulation will likely cause negative downstream effects on an unregulated party and vacatur will obviate those effects. As part of the standing inquiry, the Court assumed that a plaintiff is statutorily entitled to the remedy of vacatur. Following CASA, one wonders whether that assumption still holds. After all, much like the universal injunction, vacatur prohibits the agency from enforcing the challenged regulation against anyone, anywhere. Building on his concurrence in Corner Post, Justice Kavanaugh might respond that the “background equitable principles” underlying CASA’s repudiation of universal injunctions are inapposite because Congress departed from that “baseline” by “empowering the judiciary to act directly against the challenged agency action” through the APA. But defenders of vacatur need not concede that it is altogether foreign to equity.

A cornerstone of CASA’s approach to equity is its recognition that “the complete-relief principle has deep roots.” If a plaintiff has standing to sue and is correct on the merits, the court should make her whole. As Justice Kavanaugh noted, vacatur is the only way for unregulated parties to obtain redress for their injuries. To borrow one of his hypotheticals in Diamond Alternative Energy, suppose the FDA—trying to Make America Healthy Again—bans the sale of hot dogs in sports stadiums. As a result, Vienna Beef suffers a sharp drop in demand. A party-specific injunction does not offer any meaningful relief: the court cannot enjoin the FDA’s application of the regulation against Vienna Beef because Vienna Beef is not a regulated entity; nor can the court order sports stadiums to buy more hot dogs because sports stadiums have violated no law. For Vienna Beef to get redress, the court must enjoin the FDA’s application of the regulation against sports stadiums. That is, in effect, vacatur. And that relief is not just complete, it is the only one on the table.

While flexible, equity is not infinitely malleable. This much is clear from CASA:  Federal courts have no license to make up whatever remedies they see fit and call it “equity.” Rather, historical practice shapes what equitable remedies look like and what circumstances warrant such relief. The throughline of this history—dating back to the English Court of Chancery—is that “the broader and deeper the remedy the plaintiff wants, the stronger the plaintiff’s story needs to be.” Because it allows federal courts to erase a rule from the Code of Federal Regulations and superintend an executive agency’s conduct with respect to nonparties, vacatur is available only if strictly necessary to remediate the plaintiff’s harm—only if nothing else can make right what is wrong.

Under the APA, any person “adversely affected or aggrieved by agency action” may seek judicial review. Some plaintiffs are the direct object of the regulation; others are adversely affected by dint of their economic or other close relationship with a regulated entity. If a regulated plaintiff requests vacatur, equity erects a high hurdle because a party-specific injunction offers complete relief. A court cannot go further. But if an unregulated plaintiff requests vacatur, that remedy is in play because it is her only recourse. This is not to say that in those cases, federal courts should award vacatur as a matter of course. Equitable remedies come with equitable constraints.  Perhaps the plaintiff’s injuries are cognizable enough to establish standing but not serious enough to justify equitable intervention. Or perhaps the government can make out an equitable defense like unclean hands or estoppel. But the analysis must also account for the plaintiff’s status as an unregulated party.

This, of course, creates an incongruity between regulated and unregulated plaintiffs—vacatur is available to the latter but not the former. Standing doctrine closes the gap.  Regulated parties generally have no trouble getting into federal court. For unregulated parties, the opposite is true. Time and again, the Supreme Court has held that it is “substantially more difficult” for unregulated parties to establish standing because their injuries are contingent upon the conduct of absent third parties that the court can neither predict nor control. Standing doctrine ensures that not every agency rule is susceptible to vacatur. Many, I suspect, can only be enjoined on a party-by-party basis.

Justice Kavanaugh may well be right that federal courts have authority to vacate unlawful agency action. If so, it is equity—not the APA—that is doing the work.  When dispensed as a last resort, rather than a first impulse, vacatur fits comfortably within the broad contours of traditional equitable relief.

Brian Chen is a law clerk on the U.S. Court of Appeals for the Eleventh Circuit. Views expressed here are his alone.