Definition - What does Supplemental Jurisdiction mean?
Supplemental jurisdiction gives federal courts the power to preside over claims that they would not properly have subject matter jurisdiction over. The claims that federal courts may hear with supplemental jurisdiction must form part of the same controversy as the claims that federal courts have original jurisdiction over.
Supplemental jurisdiction is officially defined in Chapter 28 of the United States Code.
Justipedia explains Supplemental Jurisdiction
Supplemental jurisdiction gives federal courts broader powers to hear cases that would otherwise have to be decided in state or other courts. Without supplemental jurisdiction, federal courts could only hear cases involving claims that they have original, subject matter jurisdiction over. The other claims would have to be set aside for other courts to hear.
Supplemental jurisdiction helps judicial efficiency and expedites the judicial process. In practice, parties to a case may have strategic reasons for seeking jurisdiction in one court over another, and supplemental jurisdiction grants these parties an extra avenue to gain venue.