Why Supplemental Jurisdiction Exists

Why Supplemental Jurisdiction Exists

Federal courts decide subject-matter jurisdiction claim by claim, not case by case. Every claim in a district court needs its own statutory "ticket of admission," whether that ticket is § 1331, § 1332, or another statute that vests jurisdiction in the district court.¹ The reason lies in the nature of federal courts. A state court of general jurisdiction is presumed to have power over every claim joined before it, so joinder rarely raises a jurisdictional question there. A federal court has only the jurisdiction Congress confers, and no presumption fills the gap.² It follows that winning jurisdiction over claim #1 under § 1331 says nothing about claim #2, a counterclaim, or a third-party claim added later. Each of those needs a basis of its own.³

This rule collides with the joinder rules. The Federal Rules of Civil Procedure favor trying a whole dispute in one proceeding, but Rule 82 provides that the rules do not extend or limit the jurisdiction of the district courts.⁴ Imagine a plaintiff arrested by two police officers who sues each officer under 42 U.S.C. § 1983 for unreasonable seizure and adds a state-law battery claim against each. Joinder is proper, since Rule 20 allows the two officers to be sued together over the same arrest and Rule 18 allows several claims against each. The § 1983 claims arise under federal law, but the battery claims are state-law claims against defendants from the plaintiff's own state, so they have no independent basis for jurisdiction. Had the plaintiff sued on battery alone, the federal court would have dismissed.⁵

There are three ways to resolve the collision. The court could split the dispute, keeping the federal claims in federal court and sending the state claims to a state court. That is wasteful, because one court could hear the whole matter, and the same facts would be litigated twice. The court could instead send the entire case to state court, which can hear both sets of claims, but that would sharply restrict access to a federal forum for the federal claim. The third option, which Congress adopted, is to extend federal jurisdiction to the related non-federal claims so that the court can hear everything together.⁶ The efficiency gain is real, but so is the federalism cost. A rule that sweeps related state claims into federal court shifts the division of labor between the two court systems, which is why the extension needs principled limits.⁷

Two labels keep the analysis straight. The claim that satisfies a jurisdictional requirement on its own is the "anchor" claim, and its companion without an independent basis is the "supplemental" claim.⁸ Supplemental jurisdiction is never a free-standing basis for jurisdiction. It can be used only after at least one claim has found original jurisdiction under § 1331, § 1332, or another statute, and it then supplements that jurisdiction by pulling related claims in.⁹ The anchor requirement is the safeguard against abuse, since without it a purely state-law dispute between co-citizens could reach federal court just by being labeled supplemental. Contrast two plaintiffs. One who sues an employer under Title VII and adds a state wrongful-discharge claim from the same firing can bring the state claim along with the federal anchor. Another who files only a state contract claim against a co-citizen has nothing to supplement and must go to state court. A third situation needs no supplemental jurisdiction at all: when a joined claim could have been brought in federal court on its own, it carries its own ticket.¹⁰ Two questions therefore arise in every multi-claim case: whether the joinder rules permit the combination, and whether the federal court that has jurisdiction over the anchor claim also has jurisdiction over the supplemental one.¹¹

Older terminology still matters because the statute preserves some of its distinctions. Before Congress acted, courts had built the equivalent of supplemental jurisdiction through case law, under two labels. Pendent jurisdiction applied when the claims that originally entered federal court were not based solely on diversity, as when a state claim was added to a federal-question claim. Ancillary jurisdiction applied when the entering claims rested solely on diversity. Courts took pendent jurisdiction more readily and restricted ancillary jurisdiction, and § 1367 carries that preference forward.¹² The judge-made doctrines were justified by judicial economy, since the alternative was two suits in two court systems.¹³ They also raised a constitutional question, because courts appeared to be writing their own jurisdictional powers, and the federalism stakes differed depending on whether the added claim was a state claim attached to a diversity case or to a federal one.¹⁴ Congress responded in 1990 by replacing both doctrines with the single term supplemental jurisdiction in 28 U.S.C. § 1367.¹⁵

The sequence matters because a claim can satisfy the constitutional test and still fail at the statutory step, or satisfy both and still be declined as a matter of discretion. A court that skips straight to relatedness has not yet shown that any anchor claim exists.