Document ID: ./input/supremecourt_opinions/opinions/boundvolumes/558bv.pdf
Page Number: 427.0

266 

SOUTH  CAROLINA  v.  NORTH  CAROLINA 

Opinion of the Court 

ware  River’s  headwaters.  345  U. S.,  at  370.  The  Court 
granted  the  Commonwealth  of  Pennsylvania  leave  to  inter­
vene  and,  in  1931,  entered  a  decree  enjoining  certain  diver­
sions of water by the State of New York and the city of New 
York.  Id., at 371.  In 1952, the city of New York moved to 
modify  the  decree,  and  New  Jersey  and  Pennsylvania  ﬁled 
oppositions.  After  the Court  referred  the matter  to a  Spe­
cial Master, the city of Philadelphia sought leave to intervene 
on  the  basis  of  its  use  of  the  Delaware  River’s  water.  Id., 
at 371–372. 

This Court denied Philadelphia leave to intervene.  Penn­
sylvania  had  intervened  pro  interesse  suo  “to  protect  the 
rights and  interests of  Philadelphia and  Eastern Pennsylva­
nia in the Delaware River.”  Id., at 374; see also New Jersey 
v.  New  York,  283  U. S.  336,  342  (1931).  In  view  of  Pennsyl­
vania’s  participation,  the  Court  wrote  that  when  a  State  is 
“a  party  to  a  suit  involving  a  matter  of  sovereign  interest,” 
it  is  parens  patriae  and  “ ‘must  be  deemed  to  represent  all 
[of]  its  citizens.’ ”  345  U. S.,  at  372–373  (quoting  Kentucky 
v.  Indiana,  281  U. S.  163,  173–174  (1930)).  This  principle 
serves  the  twin  purposes  of  ensuring  that  due  respect  is 
given  to  “sovereign  dignity”  and  providing  “a  working  rule 
for  good  judicial  administration.”  345  U. S.,  at  373.  The 
Court,  thus,  set  forth  the  following  standard  governing  in­
tervention in an original action by a nonstate entity: 

“An  intervenor  whose  state  is  already  a  party  should 
have the burden of showing some compelling interest in 
his own right, apart from his interest in a class with all 
other citizens  and creatures of the  state, which interest 
is not properly represented by the state.”  Ibid. 

On  several  subsequent  occasions  the  Court  has  reafﬁrmed 
this “general rule.”  See Nebraska v.  Wyoming, 515 U. S. 1, 
21–22  (1995);  United  States  v.  Nevada,  412  U. S.  534,  538 
(1973)  (per  curiam);  Illinois  v.  Milwaukee,  406  U. S.  91,  97 
(1972).