Royal Canin U.S.A., Inc. v. Wullschleger, 2025 U.S. LEXIS 365 (U.S. Supreme Court, January 15, 2025) (Kagan,J.)
If a complaint filed in the state court asserts federal-law claims, the claimant may remove to federal court. If the complaint also asserts state-law claims arising from the same facts, the federal court may adjudicate those claims also in the exercise of supplemental jurisdiction. When an amendment in federal court excises the federal-law claim that enable a removal, the federal court loses its supplemental jurisdiction over the related state-law claims. The case must then return to state court.