Hain Celestial v. Palmquist: A Wrong Improper-Joinder Ruling Sends a Tried Case Back to State Court

On February 24, 2026, the U.S. Supreme Court decided The Hain Celestial Group, Inc. v. Palmquist, a unanimous opinion by Justice Sotomayor with a concurrence by Justice Thomas ¹. The question was narrow but consequential: if a federal district court wrongly dismisses the only nondiverse defendant after removal, can the resulting judgment survive because the parties were diverse by the end of the case? The Court said no ¹. The judgment must be vacated, and in this case the litigation goes back to state court ².

The Case

Sarah and Grant Palmquist fed their son baby food made by Hain Celestial Group and bought from Whole Foods Market ¹. After the child developed serious developmental disorders that some doctors attributed to heavy-metal poisoning, the family sued both companies in Texas state court, accusing Hain of negligence and product liability and accusing Whole Foods of negligence and breach of warranty ¹.

Hain, which is incorporated in Delaware and headquartered in New York, removed the case on diversity grounds ¹. Complete diversity was missing, however, because Whole Foods and the Palmquists were all Texas citizens ¹. Hain argued that Whole Foods had been improperly joined. The district court agreed, dismissed Whole Foods, denied remand and tried the case against Hain alone, then granted Hain judgment as a matter of law for lack of causation evidence ¹. The Fifth Circuit reversed the improper-joinder ruling, held that the Palmquists had plausibly alleged claims against Whole Foods, vacated the judgment and ordered the case remanded to state court ¹. The Supreme Court took the case to resolve a split among the circuits ¹.

The Holding

Federal courts are courts of limited jurisdiction, and an appellate court must confirm the lower court’s jurisdiction as well as its own ¹. If the district court lacked jurisdiction when a case was filed or removed, any merits judgment generally must be vacated ¹. The one relevant exception, from Caterpillar Inc. v. Lewis, applies when the district court cures the defect before final judgment, as when the nondiverse party in that case settled and was dismissed with all parties’ consent ¹.

That exception did not help Hain. The dismissal of Whole Foods was wrong and interlocutory, so it merged into the final judgment and was open to review ¹. When the Fifth Circuit reversed it, Whole Foods was back in the case, complete diversity was gone, and the defect “lingered through judgment” ¹. The Court rejected the argument that the parties’ diversity at judgment was enough, noting that it has never held a district court can create jurisdiction through its own mistakes ¹. It also held that the efficiency concerns in Caterpillar cannot excuse an uncured jurisdictional defect ¹.

Finally, the Court refused to let Hain use Federal Rule of Civil Procedure 21 to drop Whole Foods on appeal ¹. A defendant cannot use that rule to override the plaintiff’s choice of a state forum, and the Palmquists had properly joined a nondiverse defendant and promptly moved to remand ¹. SCOTUSblog’s summary was that, because the trial court never had jurisdiction, the entire case returns to state court ².

What It Means for Case Valuation and Settlement

The practical lesson is about risk that sits underneath the merits. After Palmquist, a defense win in federal court that depends on an improper-joinder ruling stays exposed until that ruling survives appeal ¹. Here, the defendants won at trial and still faced a new proceeding in state court ².

That changes the math in mediation:

• Defense counsel evaluating a removed case built on improper joinder should weigh the chance that a favorable result, even after trial, will be vacated if the joinder ruling is reversed ¹.
• Plaintiffs’ counsel who promptly moved to remand and preserved the issue may have more leverage than a federal loss suggests, because a reversal on joinder unwinds the judgment ¹.
• Both sides should account for the cost and delay of starting over in state court when comparing a settlement number with the expected value of continued litigation.

Jurisdictional risk rarely appears in a damages spreadsheet, but it can be the issue that decides whether years of litigation count. Palmquist makes it a factor worth putting on the table early.

Counsel looking for a Florida Supreme Court Certified Circuit Civil Mediator for a removed or remanded case can check Tony Roca’s live availability and book a mediation.