Page:Mississippi v. Tennessee (2021).pdf/3

Rh in the context of the Middle Claiborne Aquifer. To the contrary, Mississippi’s ownership approach would allow an upstream State to completely cut off flow to a downstream one, a result contrary to the Court’s equitable apportionment jurisprudence. The Court’s decision in Tarrant Regional Water Dist. v. Herrmann, 569 U. S. 614, does not support Mississippi’s position. Tarrant concerned whether one State could cross another’s boundaries to access a shared water resource under the terms of an interstate compact. The Court did not consider equitable apportionment, because the affected States had negotiated a compact that determined their respective rights to the resource. To the extent Tarrant stands for the broader proposition that one State may not physically enter another to take water in the absence of an express agreement, that principle is not implicated here. The parties have stipulated all of Tennessee’s wells are drilled straight down and do not cross the Mississippi–Tennessee border. While the origin of an interstate water resource may be relevant to the terms of an equitable apportionment, that feature alone cannot place the resource outside the doctrine itself. Because the waters contained in the Middle Claiborne Aquifer are subject to equitable apportionment, the Court overrules Mississippi’s exceptions and adopts the Special Master’s recommendation to dismiss the bill of complaint. Pp. 9–11.

, delivered the opinion for a unanimous Court.