Document ID: ./input/supremecourt_opinions/opinions/boundvolumes/558bv.pdf
Page Number: 450.0

Cite as: 558 U. S. 256 (2010) 

289 

Opinion of Roberts, C. J. 

cial  Master’s  recommendation  to  deny  intervention,  the 
Court  nonetheless  permitted  those  entities  to  participate  as 
amici.  See 507 U. S., at 589–590; Nebraska v.  Wyoming, 502 
U. S.  1055  (1992).2  The  majority  does  not  explain  why  that 
familiar  and  customary  approach  might  be  inadequate  in 
this case. 

*

*

* 

Our  original  jurisdiction  over  actions  between  States  is 
concerned with disputes so serious that they would be 
grounds  for  war  if  the  States  were  truly  sovereign.  Texas 
v.  New  Mexico,  462  U. S.,  at  571,  n.  18.  A  dispute  between 
States  over  rights  to  water  ﬁts  that  bill;  a  squabble  among 
private  entities  within  a  State  over  how  to  divvy  up  that 
State’s  share  does  not.  A  judgment  in  an  equitable  appor­
tionment  action  binds  the  States;  it  is  not  binding  with  re­
spect to particular uses asserted by private entities.  Allow­
ing intervention by such entities would vastly complicate and 
delay  already  complicated  and  lengthy  actions.  And  the 
beneﬁts private entities might bring can be readily secured, 
as  has  typically  been  done,  by  their  participation  as  amici 
curiae. 

In  light  of  all  this,  it  is  difﬁcult  to  understand  why  the 
Court grants nonsovereign entities leave to intervene in this 
equitable apportionment action, and easy to understand why 
the Court has never before done so in such a case. 

I  would  grant  South  Carolina’s  exceptions,  and  deny  the 

motions to intervene. 

2 No  party  ﬁled  exceptions  to  the  Special  Master’s  recommendation  to 
deny intervention in Nebraska v.  Wyoming.  The Special Master later al­
lowed one of the entities, Basin Electric Power Cooperative, to intervene 
as  a  party  based  on  changed  circumstances.  See  Addendum  to  Reply 
Brief  for  Duke  Energy  2–5.  That  decision  was  never  reviewed  by  the 
Court.