In an unanimous opinion by Chief Justice Roberts, the U.S. Supreme Court has rejected Mississippi’s claims of state ownership of groundwater within its territorial boundaries. The Court instead, as a matter of first impression, extended the equitable apportionment doctrine for flowing waters and resources to the disputed Memphis aquifer.
Over two decades of litigation in federal courts, Mississippi has pressed its claim of sovereign ownership of groundwater in the aquifer within its state boundaries. Based on its claim of state “ownership,” Mississippi has sought hundreds of millions of dollars for the alleged unlawful conversion of its groundwater by neighboring Tennessee. This claim of ownership is at odds with a line of Supreme Court doctrines, starting with equitable apportionment, as Chief Justice Roberts writes for the Court (slip. op., at 9-10):
Mississippi contends that it has sovereign ownership of all groundwater beneath its surface, so equitable apportionment ought not apply. We see things differently. It is certainly true that “each State has full jurisdiction over the lands within its borders, including the beds of streams and other waters.” Kansas v. Colorado, 206 U. S. 46, 93 (1907). But such jurisdiction does not confer unfettered “ownership or control” of flowing interstate waters themselves. Wyoming v. Colorado, 259 U. S. 419, 464 (1922). Thus, we have “consistently denied” the proposition that a State may exercise exclusive ownership or control of interstate “waters flowing within her boundaries.” Hinderlider v. La Plata River & Cherry Creek Ditch Co., 304 U. S. 92, 102 (1938). Although our past cases have generally concerned streams and rivers, we see no basis for a different result in the context of the Middle Claiborne Aquifer…. Mississippi’s ownership approach would allow an upstream State to completely cut off flow to a downstream one, a result contrary to our equitable apportionment jurisprudence.
Thus the Chief Justice succinctly ended the Court’s discussion of the issue and Mississippi’s nearly two-decade legal quest for ownership of groundwater within its territory as property. It is a resounding win for neighboring Tennessee, Memphis, and the Memphis Light, Gas and Water Division, vindicating their long-standing legal position that the dispute must be plead as a request for equitable apportionment before arguing the merits of their water use and impacts.
How might the opinion in Mississippi v. Tennessee shape water law? The Court is explicit that it is deciding as a matter of first impression “whether equitable apportionment applies to interstate aquifers.” (slip op., at 7.). While the Chief Justice attempts to narrow the discussion to the Middle Claiborne Aquifer at issue in this dispute, the Court’s equitable apportionment holding would apply to (1) any interstate resource with (2) a measurable flow that (3) allows one state to interfere with the resource without trespassing into another state’s territory.
Mississippi v. Tennessee thus makes clear that states do not own the groundwater within their territory, and that interstate disputes over groundwater are subject to the Court’s equitable apportionment doctrine and procedures. However, the case makes no mention of the legal basis for denying state ownership and the long-standing alternative to state ownership of waters – the public trust doctrine. The Court’s silence on this background principle is striking, especially as public trust advocates are pushing to clarify and expand the doctrine in federal courts.
In my view, the Court’s holding on the equitable apportionment doctrine is logical and sound but could have gone further. I filed an amicus brief with a small crew of water law professors (Joe Regalia, Robert Abrams, Burke Griggs, and Jesse Richardson) to share with the Court the doctrines and implications beyond equitable apportionment in considering claims of state ownership of water as property. Beginning with a law review article in 2013 (Interstate Groundwater Law in the Snake Valley: Equitable Apportionment and a New Model for Transboundary Aquifer Management, with Benjamin L. Cavataro, 2013 Utah L. Rev. 1553) and again in 2016 (Interstate Groundwater Law Revisited: Mississippi v. Tennessee, with Joseph Regalia, 34 Virginia Environmental L. J. 1520), I have advanced and detailed how equitable apportionment should and can apply to groundwater. The more difficult question is what then explains the state’s relationship to waters within its territory, if not ownership? Joe Regalia and I explored this question, with implications for public water rights and protections, in our most recent article Waters of the State (59 Nat. Res. J. 59 2019). In short, it comes back to the public trust doctrine. And with a succinct opinion in Mississippi v. Tennessee, fundamental questions about the scope and power of the public trust doctrine for our waters remain unanswered.