Mississippi v. Tennessee, No. 143, Orig.: Mississippi brought an original action against Tennessee, seeking $615 million in damages for Tennessee’s pumping from the Middle Claiborne Aquifer, which lies beneath both States. Mississippi’s complaint expressly disclaimed equitable apportionment, the doctrine applied by the Court to produce a fair allocation of a shared water resource between two and more States, and which the Court had often applied to interstate rivers and streams. The Court-appointed Special Master found that equitable apportionment is the exclusive remedy, and recommended dismissing the complaint with leave to amend. Today, the Court held that equitable apportionment of the Middle Claiborne Aquifer would be sufficiently similar to past applications of the doctrine to warrant the same treatment, but denied leave to amend as Mississippi neither sought leave to amend nor tendered a proposed amended complaint. Chief Justice Roberts issued the Court’s unanimous opinion.

View the Court's decision.