Supplemental jurisdiction

When a federal court already has jurisdiction over at least one claim, supplemental jurisdiction lets it hear related claims that on their own could only be brought in state court. The related claims have to be part of the same overall dispute, sharing a common set of facts. Federal courts have discretion to decline supplemental jurisdiction in certain situations, such as when the federal claim drops out early. The purpose is efficiency, so that one set of facts does not have to be litigated twice in two different court systems. Without this tool, plaintiffs would often have to split their cases.