Pendent party jurisdiction

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In the United States federal courts, pendent party jurisdiction refers to a court's power to adjudicate a claim against a party who would otherwise not be subject to the jurisdiction of the federal courts, because the claim arose from a common nucleus of operative fact.^[1][2]

One well-known example of this is when a federal court adjudicates a state law claim asserted against a third party which is part of a case brought to it under its federal question jurisdiction. This was the situation in Finley v. United States, 490 U.S. 545 (1989), in which the Supreme Court found that a grant of jurisdiction over a claim involving certain parties did not extend to additional claims involving different parties.^[3] Finley was superseded by Exxon Mobil Corp. v. Allapattah Services, 545 U.S. 546, in which the Supreme Court noted that Congress overturned the result in Finley by enacting 28 U.S.C. § 1367.^[4]

Pendent party jurisdiction is a form of supplemental jurisdiction covered by 28 U.S.C. § 1367. Subsection (b) prohibits parties from being joined in a federal case brought under the diversity jurisdiction of the federal courts (where diversity is the sole basis of federal court jurisdiction), if joining such parties would eliminate complete diversity.^[5]