Supplemental jurisdiction in the United States is the jurisdiction excercised by federal courts over a case regarding state law in order to resolve all the issues between the parties without having to litigate the same facts more than once.
Supplemental jurisdiction was once also referred to as ancillary jurisdiction and pendent jurisdiction. pendent jurisdiction under Mine Workers v. ...
Courts may acquire supplemental jurisdiction over other claims if they are related to a claim that has already been brought before the court in the same litigation. The federal court is not required to have an independent jurisdiction over the related claims. Supplemental jurisdiction is also discretionary, meaning that the court may elect not to exercise this jurisdiction over the other related claims. For example, if the related state claim is too complex, the federal court may not want to hear it.
Notable cases regarding supplemental jurisdiction include Russ v. State Farm Mutual Automobile Ins. Co., Fullin v. Martin, and United Mine Workers of America v. Gibbs. The rules for supplemental jurisdiction are set out in 28 US ยง 1367.