The Supreme Court recently elected to hear Barbara v. Trump. That case centers around the issue of birthright citizenship: Does the Fourteenth Amendment guarantee citizenship to the children of “unlawfully present aliens” and “temporary visitors?” The answer to that question is hugely consequential.

But this blog addresses a different question—one that has seemingly been overlooked by both parties in Barbara: Can district courts issue class-wide relief to provisional classes of plaintiffs?

The answer to this question may prove to be equally consequential for public law litigants.  In Trump v. CASA, the Supreme Court did away with the so-called “universal injunction.” To remain within the traditional bounds of equity, the Supreme Court held, federal courts can give only party-specific relief. Absent plaintiffs—who would not be bound by an adverse judgment—cannot benefit from a judgment awarded to a present plaintiff. If a litigant wants relief, she must become a proper party to the case, binding herself to the court’s judgment—win or lose.

To be sure, the CASA Court blessed the practice of awarding injunctive relief to classes of plaintiffs. Doing so is consistent with equity because the class device brings all members “before the court” as proper parties: Even if they are not physically present, they are bound by the court’s judgments. If the class wins, all class members benefit. If the class loses, no class member gets another bite at the apple.

But what about relief given to “putative” or “provisional” classes? As I note in a forthcoming piece in the Baylor Law Review, these are classes that are not yet formally certified under Rule 23. That means they are not yet “proper parties” before the court. So, “when a court gives preliminary relief to a putative class, it’s giving relief to non-parties. These non-parties receive the benefit of judgments in favor of the putative class but are not bound by adverse judgments.” Under the logic of CASA, then, courts shouldn’t be able to dole out injunctive relief to such classes. Doing so violates the equitable principles outlined and endorsed by the CASA Court.

The district court didn’t reckon with this issue in Barbara. Without much explanation, the court concluded that it could “certify classes provisionally for the purpose of injunctive relief.” And at the end of that sentence, the court dropped a footnote: “The Supreme Court has also indicated that courts can issue temporary injunctive relief to a putative class. See A.A.R.P. v. Trump, 605 U.S. 91 (2025).” The district court was right in some sense. In A.A.R.P., the Supreme Court seemingly blessed the practice of issuing preliminary relief to putative classes. But the legality of this type of relief wasn’t squarely before the Court in that case. And, crucially, A.A.R.P. was decided before CASA. “In a post-CASA world, if the Court were presented with its own arguments (made in CASA), it might question and seriously probe the validity of putative class relief.”

Some think that what the district court did here was just fine—even under CASA’s logic. Professor David Marcus, for instance, has argued that when courts say they are certifying “provisional” classes, they are still performing formal certification. The only reason courts call these classes provisional is that, under Federal Rule of Civil Procedure 23(c)(1)(C), class certification orders can always be revised down the line. In other words, all classes are in some sense provisional because all classes can be amended or altered later on. So, the argument goes, while putative classes are certainly not formally certified, provisional classes are.

Marcus is correct about the mechanics of Rule 23. But I think he’s wrong that courts are issuing bona fide, formal certification orders and just calling them “provisional.” I discuss at length why I think that’s the case in my forthcoming piece. But, for our purposes here, just consider Barbara itself. The government argued in its submissions to the district court that provisional class certification is different than formal class certification:  In the government’s eyes, the plaintiffs “s[ought] to short-circuit that normal” class certification process “and have the Court provisionally certify the class and immediately issue a class-wide preliminary injunction.” To the government, “[t]hat request [was] inappropriate.” The government argued that “[w]hile courts have provisionally certified classes to allow parties to obtain a form of preliminary and emergency relief, those circumstances [were] distinct from this case.”

The district court itself recognized that provisional class certification wasn’t just run-of-the-mill formal class certification. Recall that when it justified its issuance of relief to a provisional class, it dropped a footnote justifying its decision with reference to A.A.R.P.—a case where “temporary injunctive relief” was given to a putative class. That suggests that the district court itself viewed provisional classes as akin to putative—not formally certified—ones.

So, if provisional classes are like putative classes—because neither are formally certified—then provisional class members are not proper parties before a court. That means giving them relief—preliminary or otherwise—offends the equitable principles described by the CASA Court. To be sure, district courts can hand out class-wide preliminary relief in a manner that is consistent with CASA and with equity: “District courts can formally certify … classes under Rule 23, and, then—and only then—issue preliminary relief.” Officially certifying a class—and not just doing so “provisionally”—ensures that all class members are proper parties, bound by whatever judgment the court issues.

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Can federal courts issue relief to a class of plaintiffs that has not yet been properly certified under Federal Rule of Civil Procedure 23? That’s an important question. And it’s one that the Supreme Court did not address in CASA. As the Court addresses the scope of the Fourteenth Amendment in Barbara, it may want to clarify the scope of federal courts’ equitable powers, too.

Elias Neibart graduated from Harvard Law School in May 2025. He now works as a law clerk in New York.