Document ID: ./input/supremecourt_opinions/opinions/21pdf/143orig_1qm1.pdf
Page Number: 1

(Slip Opinion) 

OCTOBER  TERM,  2021 

1 

Syllabus 

NOTE:  Where  it  is  feasible,  a  syllabus  (headnote)  will  be  released,  as  is 
being  done  in  connection  with  this  case,  at  the  time  the  opinion  is  issued. 
The  syllabus  constitutes  no  part  of  the  opinion  of  the  Court  but  has  been 
prepared  by  the  Reporter  of  Decisions  for  the  convenience  of  the  reader. 
See United States v. Detroit Timber & Lumber Co., 200 U. S. 321, 337. 

SUPREME COURT OF THE UNITED STATES 

Syllabus 

MISSISSIPPI v. TENNESSEE ET AL. 

ON EXCEPTIONS TO REPORT OF SPECIAL MASTER 

No. 143, Orig.  Argued October 4, 2021—Decided November 22, 2021 

Mississippi  brought  an  original  action  against  Tennessee  for  damages
and other relief related to the pumping of groundwater by the City of 
Memphis  from  the  Middle  Claiborne  Aquifer,  a  valuable  water  re-
source that lies beneath eight States.  Mississippi argues that Tennes-
see’s pumping—using wells Mississippi concedes are located entirely 
in Tennessee—siphons water away from Mississippi and amounts to a
tortious taking of groundwater owned by Mississippi.  Mississippi ex-
pressly disclaims any equitable apportionment remedy, arguing that 
the “fundamental premise of this Court’s equitable apportionment ju-
risprudence—that each of the opposing States has an equality of right 
to use the waters at issue—does not apply to this dispute.”  Complaint 
¶49.  The Special Master appointed by the Court to assess Mississippi’s
claims determined that the aquifer is an interstate water resource and 
that  equitable  apportionment  is  the  exclusive  judicial  remedy.  Be-
cause  Mississippi’s  complaint  did  not  seek  equitable  apportionment, 
the Special Master recommended that the Court dismiss the complaint
but grant Mississippi leave to amend.  Mississippi challenges the rec-
ommendation to dismiss; Tennessee objects to the recommendation to
grant Mississippi leave to file an amended complaint.  

Held:  The waters of the Middle Claiborne Aquifer are subject to the ju-
dicial  remedy  of  equitable  apportionment;  Mississippi’s  complaint  is 
dismissed without leave to amend.  Pp. 7–12. 

(a)  The doctrine of equitable apportionment aims to produce a fair 
allocation of a shared water resource between two or more States, see 
Colorado v. New Mexico, 459 U. S. 176, 183, based on the principle that
States have an equal right to reasonable use of shared water resources. 
Florida v. Georgia, 592 U. S. __, __.  The Court has applied the doctrine
to interstate rivers and streams, see South Carolina v. North Carolina,