In United Mine Workers v. Gibbs, the Supreme Court rejected the narrow “cause of action” test announced in Hurn v. Oursler for what was then termed pendent-claim jurisdiction in favor of a broader “common nucleus of operative fact” standard. In subsequent cases, the Court in dicta implied, without deciding, that the same standard might govern other extensions of federal court jurisdiction to non-diverse state law claims incident to federal question or diversity claims falling within Article III of the U.S. Constitution in the related but distinct contexts of “pendent party” and “ancillary” jurisdiction. Meanwhile, cases in the lower courts tended to equate the Gibbs standard with the “same transaction or occurrence” joinder standard that pe...