This op-ed originally ran in the Memphis Commercial Appeal.
In an era when most Supreme Court opinions are sharply divided, recently the high court unanimously rejected Mississippi’s claim against Tennessee in a long-running dispute over the groundwater that lies beneath both states in a common aquifer.
The impacts of this case will extend far beyond Mississippi and Tennessee, as states compete with one another over limited water supplies.
When neighboring states fight over shared rivers, the law has been clear for more than a century: They can settle their differences either by negotiated agreements known as “interstate compacts” or they can ask the Supreme Court to divide up the waters through what is known as an “equitable apportionment.”
But until late November, it was not as clear how states should resolve brawls over water when it is found underground in geologic formations known as aquifers.
Read the full op-ed in the Memphis Commercial Appeal.
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."
The Supreme Court's decision
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 …
Mississippi v. Tennessee is not only the Supreme Court’s first oral argument of the 2021-22 term, but it is also the first time that states have asked the court to weigh in on how they should share an interstate aquifer. The court’s decision could fundamentally restructure interstate groundwater law in the United States for decades — or the case could be dismissed immediately on the grounds that Mississippi has failed to allege the proper cause of action.
The case will be argued on Monday, and it will be the court’s first in-person argument in a year and a half. In March 2020, the justices stopped meeting in person due to the coronavirus pandemic, and since then, all arguments have been conducted by phone. But the justices are returning to …