The decision could complicate states’ ability to pursue groundwater natural resource damages actions.
On November 22, 2021, the US Supreme Court held that equitable apportionment applies to a dispute between states about their respective interests in groundwater that flows through multiple states in Mississippi v. Tennessee. The decision may have implications for natural resource damages (NRD) claims. Natural resource trustees often assert claims to pursue damages to groundwater. In assessing these claims, courts often must determine (1) whether the trustee has a trusteeship interest in the groundwater resource at issue, and (2) if so, the extent of the trustee’s interest in that groundwater resource relative to the interests of other trustees in the same groundwater.