Pendent jurisdiction is the authority of a United States federal court to hear a closely related state law claim against a party already facing a federal claim, described by the Supreme Court as "jurisdiction over nonfederal claims between parties litigating other matters properly before the court." Such jurisdiction is granted to encourage both "economy in litigation

Judicial economy

Judicial economy refers broadly to the principle that the limited resources of the legal system or a given court should be conserved.-Multiple causes of action in a given case :...

", and fairness by eliminating the need for a separate federal and state trial hearing essentially the same facts yet potentially reaching opposite conclusions.

Pendent jurisdiction refers to the court's authority to adjudicate claims it could not otherwise hear. The related concept of pendent party jurisdiction

Pendent party jurisdiction

In the United States federal courts, pendent party jurisdiction refers to a court's power to adjudicate a claim against a party whom would otherwise not be subject to the jurisdiction of the federal courts, because the claim arose from a common nucleus of operative fact.One well-known example of...

 by contrast is the court's authority to adjudicate claims against a party not otherwise under the court's jurisdiction because the claim arises from the same nucleus of facts as another claim properly before the court.

The leading case on pendent jurisdiction is United Mine Workers of America v. Gibbs

United Mine Workers of America v. Gibbs

United Mine Workers of America v. Gibbs, 383 U.S. 715 , was a case in which the Supreme Court of the United States held that in order for a United States district court to have pendent jurisdiction over a state-law cause of action, state and federal claims must arise from the same "common nucleus...

, . Gibbs has been read to require that (1) there must be a federal claim (whether from the Constitution, federal statute, or treaty) and (2) the non-federal claim arises "from a common nucleus of operative fact" such that a plaintiff "would ordinarily be expected to try them in one judicial proceeding."

The holding in Gibbs has been essentially codified by Congress along with ancillary jurisdiction

Ancillary jurisdiction

Ancillary jurisdiction allows a United States federal court to hear certain claims sufficiently related to the original claim that would otherwise defeat the court's jurisdiction...

 in , its supplemental jurisdiction

Supplemental jurisdiction

Supplemental jurisdiction is the authority of United States federal courts to hear additional claims substantially related to the original claim even though the court would lack the subject-matter jurisdiction to hear the additional claims independently. is a codification of the Supreme Court's...

statute. However, Subsection § 1367 (c)(3) "expressly authorizes the district judge to dismiss a supplemental claim when the federal claims have dropped out of the case."