Document ID: ./input/supremecourt_opinions/opinions/boundvolumes/558bv.pdf
Page Number: 438

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

277 

Opinion of Roberts, C. J. 

The result is literally unprecedented: Even though equita­
ble apportionment actions are a signiﬁcant part of our origi­
nal docket, this Court has never before granted intervention 
in  such  a  case  to  an  entity  other  than  a  State,  the  United 
States, or an Indian tribe.  Never.  That is because the ap­
portionment  of  an  interstate  waterway  is  a  sovereign  dis­
pute,  and  the  key  to  intervention  in  such  an  action  is  just 
that—sovereignty.  The  Court’s  decision  to  permit  nonsov­
ereigns to intervene in this case has the potential to alter in 
a  fundamental  way  the  nature  of  our  original  jurisdiction, 
transforming  it  from  a  means  of  resolving  high  disputes  be­
tween  sovereigns  into  a  forum  for  airing  private  interests. 
Given  the  importance  of  maintaining  the  proper  limits  on 
that jurisdiction, I respectfully dissent. 

I 

Two  basic  principles  have  guided  the  exercise  of  our  con­
stitutionally  conferred  original  jurisdiction.  The  ﬁrst  is 
an  appreciation  that  our  original  jurisdiction,  “delicate  and 
grave,”  Louisiana  v.  Texas,  176  U. S.  1,  15  (1900),  was 
granted  to  provide  a  forum  for  the  peaceful  resolution  of 
weighty  controversies  involving  the  States.  “The  model 
case  for  invocation  of  this  Court’s  original  jurisdiction  is  a 
dispute  between  States  of  such  seriousness  that  it  would 
amount  to  casus  belli  if  the  States  were  fully  sovereign.” 
Texas  v.  New  Mexico,  462  U. S.  554,  571,  n.  18  (1983).  In 
determining whether to exercise original jurisdiction, we ac­
cordingly  focus  on  “the  nature  of  the  interest  of  the  com­
plaining  State,”  and  in  particular  the  “seriousness  and  dig­
nity”  of  the  claim  asserted.  Mississippi  v.  Louisiana,  506 
U. S. 73, 77 (1992) (internal quotation marks omitted). 

Original  jurisdiction  is  for  the  resolution  of  state  claims, 
not  private  claims.  To  invoke  that  jurisdiction,  a  State 
“must,  of  course,  represent  an  interest  of  her  own  and  not 
merely  that  of  her  citizens  or  corporations.”  Arkansas  v. 
Texas, 346 U. S. 368, 370 (1953); see Kansas v.  Colorado, 533