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Posted April 2026In a July 2025 article, I discussed the Fifth Circuit’s decision in Hain Celestial Group, Inc. v. Palmquist and the Supreme Court’s grant of certiorari. A unanimous U.S. Supreme Court has now affirmed the Fifth Circuit’s decision, confirming that a district court’s erroneous dismissal of a nondiverse defendant does not cure the lack of diversity jurisdiction that existed at the time of removal. Even after a full federal trial and a defense judgment as a matter of law, the judgment could not stand, and the case had to be sent back to state court. In a decision that is likely to matter well beyond the instant case, the Court reinforced the limits of federal jurisdiction, clarified the reach of Caterpillar Inc. v. Lewis, and signaled that aggressive improper-joinder removals can carry significant risk.
The Palmquists sued Hain and Whole Foods in Texas state court after alleging that baby food manufactured by Hain and purchased at Whole Foods exposed their child to toxic heavy metals. They asserted product liability and negligence claims against Hain and breach-of-warranty and negligence claims against Whole Foods. That pleading posture mattered because the plaintiffs were Texas citizens, Hain was a citizen of Delaware and New York, and Whole Foods was a Texas citizen. As filed, the case lacked complete diversity.
Hain removed the case anyway, arguing that Whole Foods had been improperly (or fraudulently) joined and should be dismissed. The district court agreed, denied remand, dismissed Whole Foods, and kept the case in federal court. The case then proceeded to trial against Hain alone, where the district court granted judgment as a matter of law for Hain on causation grounds.
The key appellate issue was whether that federal judgment could survive if the improper joinder ruling turned out to be wrong. The Fifth Circuit held that Whole Foods had been properly joined, reversed the dismissal, vacated the defense judgment, and ordered the case remanded to state court. That ruling created the question the Supreme Court agreed to resolve: whether a district court’s final judgment as to diverse parties must be vacated when the appellate court later determines that the district court erred by dismissing a nondiverse defendant after removal.
The Supreme Court unanimously affirmed. Writing for the Court, Justice Sotomayor began with two premises: (1) no one asked the Court to revisit the Fifth Circuit’s conclusion that the district court’s improper joinder decision was incorrect and Whole Foods should not have been dismissed, and (2) no one disputed that the district court would have lacked jurisdiction had it correctly decided the joinder issue at the outset. From there, the question was narrow: Given the district court’s erroneous dismissal of Whole Foods, did the district court have jurisdiction to enter a final judgment as to Hain? The Court held that it did not.
The Court framed the case against the backdrop of ordinary jurisdictional principles. Federal appellate courts generally assess jurisdiction based on the facts existing at filing or removal. If jurisdiction was absent at that time, a merits judgment ordinarily must be vacated. The Court recognized the familiar exception from Caterpillar Inc. v. Lewis: when a jurisdictional defect is properly cured before final judgment, the judgment may stand. But the Court held that Hain fell outside that exception because Whole Foods was not properly and finally dismissed from the case. Its dismissal was erroneous and interlocutory, which meant it did not dispose of the whole case and was reversible on appeal from a final judgment in Hain’s favor. In the Court’s formulation, Whole Foods was only “temporarily and erroneously removed”; it was not “gone for good.” Because the defect therefore “lingered through judgment,” the judgment “must be vacated.”
The Court also rejected Hain’s argument that efficiency and finality should save the judgment. Although Caterpillar recognized that finality, efficiency, and economy can become “overwhelming” after a case has been tried in federal court, those concerns matter only after a jurisdictional defect has been properly and finally cured. They cannot supply jurisdiction where it never validly existed. The Court made the point plainly: a district court cannot create jurisdiction through its own mistakes.
The Court likewise rejected Hain’s fallback argument under Rule 21, which allows a federal court “on its own” to “add or drop a party” “on just terms.” While Rule 21 allows dismissal of a dispensable nondiverse party in appropriate circumstances, the Court held that the requested use of Rule 21 here would improperly override the plaintiffs’ forum choice. The Court emphasized that the plaintiff is the “master of the complaint” and that the Palmquists had purposefully and properly joined a nondiverse defendant and promptly moved to remand. Rule 21, the Court held, could not be used to force them into federal court under those circumstances.
Justice Thomas joined the Court’s opinion in full but wrote separately to express skepticism about the modern improper-joinder doctrine itself. In his view, the doctrine appears to permit federal courts to enlarge their own jurisdiction by assessing the merits of claims over which they lack jurisdiction. He suggested that the Court’s earlier fraudulent-joinder precedents were aimed at bad faith or actual fraud, not the more common modern practice of evaluating whether the plaintiff’s claims against the nondiverse defendant are sufficiently strong on the merits. He concluded that, in a future case, the Court should consider the propriety of the improper-joinder doctrine.
The Court’s majority opinion assumed the propriety of improper joinder and resolved only the narrower vacatur question. Justice Thomas, by contrast, flagged a deeper structural concern: whether federal courts should be conducting what amounts to a merits-based screening of claims against nondiverse defendants at all while jurisdiction remains in dispute. Plaintiff-side litigants will almost certainly cite the concurrence in future remand battles, and defense counsel should expect closer scrutiny of the doctrinal foundations of improper joinder going forward. If that issue eventually returns to the Court squarely presented, Hain may prove important not only for what it held, but for the broader challenge to the improper joinder doctrine that Justice Thomas’ concurrence invited.
The Supreme Court’s holding in Hain is straightforward: an erroneous dismissal of a nondiverse defendant does not cure a removal defect that existed from the beginning, and a final federal judgment cannot stand when that defect remains uncured through judgment.
For plaintiffs’ attorneys, Hain is a meaningful forum-preservation decision. It confirms that when a plaintiff properly joins a nondiverse defendant and timely contests removal, an erroneous improper-joinder ruling does not become harmless simply because the case proceeds through years of federal litigation. If the ruling is reversed on appeal, the federal judgment may still be wiped away. At the same time, the decision does not insulate weak or sham claims. The Court’s analysis depended on the premise that Whole Foods was properly joined in the first place.
For defense attorneys, Hain does not eliminate improper-joinder removals, but it does raise the stakes. Defendants considering removal on that theory now face a clearer risk that a federal merits victory may later be vacated if the joinder ruling does not hold up on appeal. That practical risk may push defendants to be more selective in asserting improper joinder and to sharpen the record on why the joinder is improper.
More broadly, the decision is an important reminder about access to federal courts. Hain underscores that federal courts are courts of limited jurisdiction and that convenience cannot expand the scope of federal judicial power beyond the limits Congress imposed. At bottom, the Court treated the case as a separation-of-powers and forum-allocation decision, not merely a technical dispute over removal mechanics. And Justice Thomas’ dissent signals that the Court may be willing—at least in a future case—to take a harder look at improper joinder itself.
For parties litigating in removed diversity cases, Hain is a reminder that jurisdictional rulings at the outset of a case can carry consequences all the way through trial and appeal. And for practitioners on both sides of the bar, the decision is a useful caution: a federal victory obtained after an erroneous removal may not be a final victory at all.
