Why It Matters

The Supreme Court's 2025 ruling in Trump v. CASA, Inc. was supposed to be a win for the Trump administration. The Court curtailed the use of nationwide injunctions, the sweeping court orders that had repeatedly blocked the administration's policies on immigration, birthright citizenship, and more. But a new Congressional Research Service report published June 5 makes clear that the victory may be narrower than it appeared.

The report, Class Action Lawsuits and Classwide Injunctive Relief, lays out how plaintiffs have already adapted, using class action litigation as a vehicle to achieve relief that is "functionally equivalent" to the nationwide injunctions the Court just restricted. The same broad judicial relief the administration fought to eliminate may be returning through a different procedural door.

The Big Picture

Class Action Lawsuits Fill the Void

When the Supreme Court ruled in CASA that nationwide injunctions were unlawful, it simultaneously described them as a "class-action workaround." Courts had been issuing sweeping orders without requiring plaintiffs to go through the procedural rigor of Federal Rule of Civil Procedure 23, the rule governing class certification in federal courts. The majority's logic was that if plaintiffs want broad relief, they should have to earn it by satisfying Rule 23's requirements.

What the Court did not do was change the rules around classwide injunctive relief itself. A properly certified class can still obtain an injunction that covers every member of that class, and if the class is defined broadly enough, that injunction can cover millions of people nationwide.

That is precisely what has happened. In the CASA litigation itself, after the Supreme Court invalidated the original nationwide injunctions blocking Executive Order No. 14160, the Birthright Citizenship Executive Order, plaintiffs sought and obtained class certification for a class defined as all children nationwide whose parents met the criteria for having citizenship withheld under the order. The district court issued a classwide preliminary injunction. As of the date of the CRS report, that injunction remains in place.

Similar class-based challenges have followed in rapid succession. Courts have certified classes of unaccompanied migrant children in federal custody, Venezuelan nationals facing deportation under the Alien Enemies Act, and individuals arrested in the District of Columbia for alleged immigration violations without a warrant.

The Rule 23 Gauntlet

Class action certification is not automatic. Under Rule 23(a), plaintiffs must satisfy four requirements: numerosity (the class is too large for individual joinder); commonality (shared questions of law or fact); typicality (the representative plaintiff's claims are typical of the class); and adequacy of representation. Courts must conduct what the Supreme Court has called a "rigorous analysis" before certifying.

The CRS report notes that class certification can be expensive and time-consuming, and that courts have interpreted these requirements more strictly since the early 2010s, particularly following Wal-Mart Stores, Inc. v. Dukes in 2011. Justice Sotomayor, in her CASA dissent, acknowledged class actions as an "important tool" but said they are not a "perfect substitute" for nationwide injunctions, citing the "higher cost of pursuing class relief" and the "difficult and time consuming" process of satisfying Rule 23(a)'s prerequisites.

Other legal scholars are pushing back. The CRS report cites experts who argue that class action litigation remains a "potent and viable substitute" for nationwide injunctions, and that courts have "overwhelmingly favored class certification" in cases challenging "uniform, across-the-board policies whose legality can be determined for everyone at once." The debate is unresolved, and the Supreme Court has not yet weighed in on the post-CASA wave of class certifications.

The Uncertified Class Problem

A separate and legally murkier question involves injunctive relief issued to putative classes before certification even occurs. In A.A.R.P. v. Trump, the Supreme Court itself temporarily enjoined the deportation of a group of Venezuelan nationals without first requiring class certification, reasoning that it needed to preserve its own jurisdiction given the imminent risk of deportation.

The CRS report notes that this ruling appears to be in tension with CASA, which was issued just one month later. The Eighth Circuit, in Tincher v. Noem, has already stayed a district court's grant of relief to an uncertified class, stating that such relief is "just a universal injunction by another name." Whether the Supreme Court would approve of pre-certification injunctive relief outside the specific circumstances of A.A.R.P. remains an open question.

Political Stakes

For the Administration

The Trump administration won a landmark ruling in CASA, only to watch plaintiffs pivot almost immediately to class action mechanisms that achieve comparable results. The administration has appealed the classwide injunction in the birthright citizenship case to the Fourth Circuit, but that appeal is currently in abeyance pending Supreme Court review of related cases. The practical effect is that the Birthright Citizenship Executive Order remains blocked more than a year after it was signed.

For Republicans

The CRS report highlights a specific legislative vehicle already in motion. On April 9, 2025, the House passed H.R. 1526, the No Rogue Rulings Act, which would limit federal district courts to issuing injunctions only against parties to a case. It would allow broader relief only from three-judge panels in cases brought by two or more states in different circuits challenging executive branch actions. The bill has not passed the Senate. The CRS report implicitly frames the bill's limitations, in that it addresses injunctions generally but does not directly resolve the class certification question.

Justice Alito's concurrence in CASA wrote that nationwide injunctions "will return from the grave under the guise of 'nationwide class relief'" if district courts certify broad classes without "scrupulous adherence to the rigors of Rule 23." That framing gives congressional Republicans a legal argument for further legislation targeting class certification standards in government-challenge cases.

For Democrats

The class action mechanism has become the primary litigation tool for challenging administration policies in the post-CASA environment, and it is working. Courts have issued classwide preliminary injunctions in multiple high-profile cases. The procedural path is harder and more expensive than obtaining a nationwide injunction, but the outcomes have been comparable in several instances.

As more of these class certifications work through the judicial system, the risk for Democrats and advocacy organizations is that the Supreme Court may impose stricter standards specifically on government-challenge class actions. The Court has not yet addressed the wave of post-CASA class certifications, and its eventual ruling could significantly constrain this tool.

For the Public

At stake is whether the courts can continue to function as a check on executive branch policies that affect large numbers of people simultaneously. If class certification becomes too difficult or too slow, individuals affected by contested government policies may have no practical recourse while litigation proceeds. If class certification becomes too easy, the CASA ruling's intended effect of disciplining judicial overreach through nationwide injunctions is substantially undermined.

The Bottom Line

The CRS report makes clear that the legal landscape after CASA is not settled. Plaintiffs have moved quickly and successfully to use class action lawsuits as a substitute for the nationwide injunctions the Supreme Court restricted, and courts have granted classwide injunctive relief that covers large nationwide populations in several cases.

Congress has two available levers. It can legislate to tighten class certification standards in cases challenging government policies, or it can go further and directly limit the geographic scope of classes certified against the federal government. The CRS report notes that Congress has done both in other contexts, including a provision in the immigration code that strips courts of authority to certify classes in certain removal order cases.

The question is how the Supreme Court will ultimately respond. As more post-CASA class certifications reach the justices, the Court will have to decide whether the class action mechanism has effectively restored the nationwide injunction through the back door, and whether that is something Rule 23 permits or something that requires correction.

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