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,, 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over a claim involving certain parties did not extend to additional claims involving different parties.[3] Finley was superseded by Exxon Mobil Corp.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 . 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]