Hain Celestial Group v. Palmquist

A federal court cannot create jurisdiction over a lawsuit through its own erroneous ruling, and when an appellate court reverses a district court's mistaken dismissal of a party who destroyed complete diversity—meaning all plaintiffs and defendants must be from different states for federal court to hear the case—the jurisdictional defect never disappears and any trial verdict must be thrown out. Justice Sonia Sotomayor authored the unanimous majority opinion. Federal courts can hear a lawsuit between citizens of different states only if every plaintiff is from a different state than every defendant—a requirement called "complete diversity." When a defendant moves a case from state court to federal court ("removal"), that diversity must exist at the moment of removal. If it does not, an appellate court reviewing the case can excuse that original defect only if the district court genuinely fixed it before trial ended—for example, by properly dismissing the nondiverse party with everyone's agreement, as happened in Caterpillar Inc. v. Lewis (1996). A defect that is never truly fixed is said to "linger through judgment," which requires the appellate court to void the verdict entirely. Here, the district court's dismissal of Whole Foods—a Texas company sued alongside the Texas-citizen plaintiffs—was an interlocutory order, meaning it did not fully resolve the case and remained open to reversal on appeal. When the Fifth Circuit reversed that dismissal as incorrect, Whole Foods was legally restored to the case, and the parties were no longer completely diverse. The jurisdictional defect had therefore never been cured. Hain argued that efficiency justified preserving the verdict because the parties happened to be fully diverse at the moment the final judgment was entered. That argument fails because no principle of law allows a court to manufacture jurisdiction through its own mistake—permitting that would let courts expand their own power beyond the limits Congress set. Hain also asked the appellate court to use Federal Rule of Civil Procedure 21 to drop Whole Foods from the case and salvage the verdict. That remedy was unavailable here because plaintiffs, not defendants, hold the right to choose their forum and to decide whom to sue. The Palmquists deliberately sued Whole Foods—a Texas company—precisely to keep the case in state court, and they promptly moved to send it back there. Allowing a competing defendant to forcibly drop Whole Foods over the plaintiffs' objection would strip the plaintiffs of their recognized right to control the structure of their own lawsuit. Justice Clarence  Thomas concurred in full but wrote separately to flag his skepticism of the "improper joinder" doctrine itself, arguing that federal courts likely cannot expand their own jurisdiction by assessing the merits of claims against nondiverse parties before deciding whether they have power to hear the case at all, and inviting a future case to squarely address that doctrine's validity.