Mississippi v. Tennessee

What is the case of Mississippi v. Tennessee?

Mississippi v. Tennessee is a case that was argued before the Supreme Court of the United States on October 4, 2021. At the time of writing of this article, a decision has not been released. The plaintiff is the State of Mississippi and the respondent is the State of Tennessee. 

See What is the Difference Between a Plaintiff and a Respondent?

Mississippi and Tennessee are in a legal dispute over a groundwater aquifer, the Middle Claiborne Aquifer, from which Tennessee has been siphoning water. Mississippi claims that the groundwater is an intrastate resource, and thus Tennessee’s siphoning would be illegal and Mississippi would be entitled to relief and damages. Tennessee argues that the aquifer is an interstate resource, and that it is thus entitled to an equitable sharing agreement under federal law.

What is the fundamental question of Mississippi v. Tennessee?

The fundamental questions of Mississippi v. Tennessee, as posed by Oyez, are:

1. Does Mississippi have sole sovereign authority over and control of groundwater naturally stored within its borders?

2. Is Mississippi entitled to damages, injunctive, and other equitable relief for the groundwater taken by Tennessee?

More broadly, however, the question of Mississippi v. Tennessee relates to state sovereignty and where state control of resources ends. This case will likely be resolved by an adjudication of whether the Middle Claiborne Aquifer counts as an interstate resource or not. The concept of an interstate resource comes most clearly from the landmark 1824 Supreme Court case of Gibbons v. Ogden, which used the Commerce Clause of the U.S. Constitution to declare federal sovereignty over resources that are shared by multiple states. Gibbons v. Ogden established the authority by which the federal government can regulate rivers, air, and other such natural resources. Mississippi v. Tennessee is ultimately a question of state vs. federal sovereignty over groundwater. 

The potential impacts of Mississippi v. Tennessee

No matter how Mississippi v. Tennessee is resolved, the case will constitute a major development in U.S. water law, which has become all the more important in light of continuing droughts in many Western states and the looming threat of climate change. 

If the Court rules in favor of Mississippi and declares that groundwater is indeed protected by state sovereignty, the stage may well be set for future interstate litigation over precious water resources. It is often difficult to distinguish between groundwater and surface water, and if a state can assert exclusive control over the former but not the latter, it will likely sue often in order to protect its water wherever it can. In a world in which water is growing ever more scarce, a ruling in favor of Mississippi could dramatically alter the balance of interstate water relations.

If, on the other hand, the Court rules for Tennessee, groundwater will be treated similarly to surface water and be subject to the doctrine of equitable apportionment. A ruling in favor of Tennessee would likely be a victory for long term state cooperation on the issues of water-sharing and climate change, but could potentially alter the status quo for certain states that currently exercise control over groundwater aquifer resources.


For more detailed discussion of these impacts, see the Legal Information Institute’s article.