If a plaintiff has both federal and state claims, although there may be no diversity jurisdiction, the federal court may exercise pendent jurisdiction over the state claim if both claims arise out of the same set of facts "common nucleus of operative fact.". This assumes that the claims would normally be expected to be tried in one judicial proceedings, which gives the federal court the power to hear the whole case.
Gibbs was awarded compensatory and punitive damages in an action against United Mine Workers union for alleged violations of federal law governing unfair labor practices. The employee brought his action in federal court in connection with a state court action for unlawful conspiracy and unlawful boycott. The suit stemmed from the conduct of union members, who, through violent means, forcibly prevented the opening of a mine operation supervised by the employee. The Court held that even assuming pendent jurisdiction was proper in the case, reversal was required due to the employee's failure to meet special proof requirements imposed by federal law, which required proof that the union ratified the acts of its members.
Was the court’s exercise of pendent jurisdiction over the federal and state claims proper?
The District Court had the power to exercise pendent jurisdiction over the plaintiff's nonfederal claims especially when such action stems from a single cause of action. It was not error to refuse to dismiss such claims. Where the consequences of peaceful and violent conduct are separable, recovery under state law may be had only for the latter. Reversal of the award of damages was necessary because "clear proof" was lacking.