Federal jurisdiction can disappear even after years of litigation, extensive discovery, and, in some cases, a completed trial. The U.S. Supreme Court underscored that reality in Hain Celestial Group, Inc. v. Palmquist, 607 U.S. 421 (2026), and Royal Canin U.S.A., Inc. v. Wullschleger, 604 U.S. 22 (2025). Although the cases involved different jurisdictional theories (diversity jurisdiction in one and federal-question jurisdiction in the other), the Court reached the same conclusion: concerns of efficiency, finality, and judicial economy cannot justify retaining jurisdiction when the statutory requirements for federal jurisdiction are not met.
Hain Celestial: An Erroneous Dismissal Cannot Create Diversity Jurisdiction
Hain Celestial Group, Inc. v. Palmquist, 607 U.S. 421 (2026), arose from a product liability action alleging that toxic heavy metals in baby food caused severe developmental injuries.
Sarah and Grant Palmquist sued Hain Celestial Group, Inc. and Whole Foods Market, Inc. in Texas state court. Hain was a citizen of Delaware and New York because it was incorporated in Delaware and maintained its principal place of business in New York. Whole Foods, however, was a Texas citizen, as were the plaintiffs. Therefore, complete diversity did not exist.
Hain nevertheless removed the case to federal court, arguing that plaintiffs’ claims against Whole Foods were not viable and that Whole Foods had therefore been improperly joined. The district court agreed, dismissed Whole Foods, denied the plaintiffs’ motion to remand, and retained jurisdiction over the case. The litigation proceeded through discovery and a jury trial. After the plaintiffs rested, the district court entered judgment as a matter of law in Hain’s favor, finding insufficient evidence of causation.
The Fifth Circuit reversed. It concluded that the plaintiffs had plausibly alleged that Whole Foods negligently misrepresented Hain’s products as safe for consumption and therefore had been properly joined. Because Whole Foods remained a Texas defendant, complete diversity never existed. The Fifth Circuit accordingly vacated the judgment and remanded the case to state court.
The Supreme Court unanimously affirmed. Writing for the Court, Justice Sotomayor explained that the district court’s erroneous dismissal of Whole Foods did not cure the jurisdictional defect that existed at the time of removal. The Court rejected the argument that jurisdiction should be deemed proper because the parties were diverse at the time final judgment was entered. The Court explained that a district court cannot create federal jurisdiction “through its own mistakes.”
The Court acknowledged that substantial resources had already been invested in the litigation, but it concluded that considerations of efficiency and finality could not overcome the absence of federal jurisdiction. As the Court emphasized, an uncured jurisdictional defect requires vacatur regardless of how much time and effort the parties have already expended.
(Justice Thomas wrote a separate concurrence questioning whether the improper-joinder doctrine rests on a sound statutory foundation. His opinion suggests that the doctrine itself may face renewed scrutiny in future cases.)
Royal Canin: Amending Away Federal Jurisdiction
The foundation for Palmquist was laid one year earlier in Royal Canin U.S.A., Inc. v. Wullschleger, 604 U.S. 22 (2025). Like Palmquist, it involved allegedly deceptive marketing of a product, in this case prescription dog food.
The plaintiff filed suit in Missouri state court alleging deceptive marketing practices relating to that dog food. Her complaint asserted claims under Missouri law and also alleged violations of the Federal Food, Drug, and Cosmetic Act, creating a basis for federal-question jurisdiction. The defendant removed the action to federal court. The plaintiff then amended her complaint to eliminate all federal allegations, leaving only state-law claims, and sought remand.
The Supreme Court unanimously affirmed the Eighth Circuit, which required a remand to state court. Writing for the Court, Justice Kagan explained that jurisdiction must be evaluated based on the operative complaint. Once the plaintiff amended her pleading to eliminate all federal claims, no basis for federal-question jurisdiction remained. The federal court likewise lost supplemental jurisdiction over the remaining state-law claims. The case therefore had to be returned to state court.
Central to the Court’s analysis was the principle that the plaintiff is “the master of the complaint.” Because plaintiffs control which claims they assert, they also exert substantial control over whether federal jurisdiction exists in the first place.
Practical Implications
In both cases, the Supreme Court made clear that considerations of efficiency, finality, and judicial economy must yield to Congress’s limits on federal jurisdiction. The decisions also reinforce the plaintiff’s substantial role in determining forum. Whether through the joinder of a non-diverse defendant or the decision to abandon federal claims, plaintiffs retain significant control over whether federal jurisdiction exists. Defendants seeking removal should therefore carefully evaluate jurisdictional issues at the outset and continue to monitor them throughout the case. As Palmquist demonstrates, even years of federal litigation and a favorable judgment may ultimately prove meaningless if federal jurisdiction is lacking.