In Dispute over Groundwater, Court Tells Mississippi It's Equitable Apportionment or Nothing

Less than two months after oral argument, in its first interstate groundwater case, the Supreme Court unanimously decided that Mississippi must rely on a doctrine known as equitable apportionment if it wants to sue Tennessee over the shared Middle Claiborne Aquifer. In an opinion by Chief Justice John Roberts, the court squarely rejected Mississippi's claim that Tennessee is stealing Mississippi's groundwater, noting that it had "'consistently denied' the proposition that a State may exercise exclusive ownership or control of interstate waters." As expected, the court's opinion in Mississippi v. Tennessee is short -- 12 pages, half of which recount the long history of the case. Nevertheless, in this first opinion about states' rights to interstate aquifers, the court made three important decisions that are likely to guide future interstate disputes over natural resources.