(Slip Opinion)              OCTOBER TERM, 2009                                       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

           SOUTH CAROLINA v. NORTH CAROLINA

  ON EXCEPTIONS TO THE REPORT OF THE SPECIAL MASTER

 No. 138, Orig. Argued October 13, 2009—Decided January 20, 2010
South Carolina brought this original action seeking an equitable appor
  tionment with North Carolina of the Catawba River’s (river) waters.
  The Court referred the matter to a Special Master, together with the
  motions of three nonstate entities—the Catawba River Water Supply
  Project (CRWSP), Duke Energy Carolinas, LLC (Duke Energy), and
  the city of Charlotte, N. C.—seeking leave to intervene as parties.
  South Carolina opposed the motions. After a hearing, the Special
  Master granted all three motions and, on South Carolina’s request,
  memorialized her reasoning in a First Interim Report. Among other
  things, she recognized that New Jersey v. New York, 345 U. S. 369,
  373, sets forth the “appropriate” standard for a nonstate entity’s in
  tervention in an original action; looked beyond intervention to origi
  nal actions in which the Court allowed complaining States to name
  nonstate entities as defendants in order to give that standard con
  text; “distilled” from the cases a broad rule governing intervention;
  and applied that rule to each of the proposed intervenors. South
  Carolina presented exceptions.
Held: The CRWSP and Duke Energy have satisfied the appropriate
 intervention standard, but Charlotte has not. Pp. 6–18.
    (a) Under New Jersey v. New York, “[a]n 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 prop
 erly represented by the state.” 345 U. S., at 373. That standard ap
 plies equally well in this case. Although high, the standard is not in
 surmountable. See, e.g., Oklahoma v. Texas, 258 U. S. 574, 581. The
 Court declines to adopt the Special Master’s proposed intervention
 rule, under which nonstate entities may become parties to original
 disputes in appropriate and compelling circumstances, such as
2               SOUTH CAROLINA v. NORTH CAROLINA

                                  Syllabus

    where, e.g., the nonstate entity is the instrumentality authorized to
    carry out the wrongful conduct or injury for which the complaining
    State seeks relief. A compelling reason for allowing citizens to par
    ticipate in one original action is not necessarily a compelling reason
    for allowing them to intervene in all original actions. Pp. 6–11.
       (b) This Court applies the New Jersey v. New York standard to the
    proposed intervenors. Pp. 11–18.
         (1) The CRWSP should be allowed to intervene. It is an unusual
    bistate entity that is jointly owned and regulated by, and supplies
    water from the river to, North Carolina’s Union County and South
    Carolina’s Lancaster County. It has shown a compelling interest in
    protecting the viability of its operations, which are premised on a fine
    balance between the joint venture’s two participating counties. The
    stresses this litigation would place on the CRWSP threaten to upset
    that balance. Moreover, neither State has sufficient interest in main
    taining that balance to represent the full scope of the CRWSP’s inter
    ests. The complaint attributes a portion of the total water transfers
    alleged to have harmed South Carolina to the CRWSP, but North
    Carolina cannot represent the joint venture’s interests, since it will
    likely respond to the complaint’s demand for a greater share of the
    river’s water by taking the position that downstream users—such as
    Lancaster County—should receive less water. See, e.g., Colorado v.
    New Mexico, 459 U. S. 176, 186–187. Any disruption to the CRWSP’s
    operations would increase—not lessen—the difficulty of achieving a
    “just and equitable” allocation in this dispute. See Nebraska v. Wyo
    ming, 325 U. S. 589, 618. Pp. 11–14.
         (2) Duke Energy should also be permitted to intervene. It has
    carried its burden of showing unique and compelling interests: It op
    erates 11 dams and reservoirs in both States that generate electricity
    for the region and control the river’s flow; holds a 50-year federal li
    cense governing its hydroelectric power operations; and is the entity
    that orchestrated a multistakeholder negotiation process culminating
    in a Comprehensive Relicensing Agreement (CRA), signed by 70 enti
    ties from both States, which sets the terms under which Duke Energy
    has applied to renew its license. These interests will be relevant to
    the Court’s ultimate decision, since it is likely that any equitable ap
    portionment of the river will need to take into account the amount of
    water that Duke Energy needs to sustain its operations. And, there
    is no other similarly situated entity on the river, setting Duke’s in
    terests apart from the class of all other citizens of the States. Just as
    important, Duke Energy has a unique and compelling interest in pro
    tecting the terms of its license and as the entity that orchestrated the
    CRA, which represents a consensus regarding the appropriate mini
    mum continuous flow of river water into South Carolina under a va
                     Cite as: 558 U. S. ____ (2010)                      3

                                Syllabus

  riety of natural conditions and the conservation measures to be taken
  during droughts. Moreover, neither State is situated to properly rep
  resent Duke Energy’s compelling interests. Neither has signed the
  CRA or expressed an intention to defend its terms, and, in fact, North
  Carolina intends to seek its modification. Pp. 14–16.
       (3) However, because Charlotte’s interest is not sufficiently
  unique and will be properly represented by North Carolina, the city’s
  intervention is not required. Charlotte is a North Carolina munici
  pality, and for purposes of this litigation, its water transfers from the
  river basin constitute part of that State’s equitable share. While the
  complaint names Charlotte as an entity authorized by North Caro
  lina to carry out a large water transfer from the river basin, the com
  plaint does not seek relief against Charlotte directly, but, rather,
  seeks relief against all North Carolina-authorized water transfers in
  excess of that State’s equitable share. Charlotte, therefore, occupies
  a class of affected North Carolina water users, and the magnitude of
  its authorized transfer does not distinguish it in kind from other class
  members. Nor does Charlotte represent interstate interests that fall
  on both sides of this dispute, as does the CRWSP. Pp. 16–18.
Exceptions to Special Master’s First Interim Report overruled in part
  and sustained in part.

  ALITO, J., delivered the opinion of the Court, in which STEVENS,
SCALIA, KENNEDY, and BREYER, JJ., joined. ROBERTS, C. J., filed an
opinion concurring in the judgment in part and dissenting in part, in
which THOMAS, GINSBURG, and SOTOMAYOR, JJ., joined.
                       Cite as: 558 U. S. ____ (2010)                              1

                            Opinion of the Court

    NOTICE: This opinion is subject to formal revision before publication in the
    preliminary print of the United States Reports. Readers are requested to
    notify the Reporter of Decisions, Supreme Court of the United States, Wash­
    ington, D. C. 20543, of any typographical or other formal errors, in order
    that corrections may be made before the preliminary print goes to press.


SUPREME COURT OF THE UNITED STATES
                                  _________________

                                 No. 138, Orig.
                                  _________________


 STATE OF SOUTH CAROLINA, PLAINTIFF v. STATE 

             OF NORTH CAROLINA 

 ON EXCEPTIONS TO THE REPORT OF THE SPECIAL MASTER
                              [January 20, 2010]

   JUSTICE ALITO delivered the opinion of the Court.
   The State of South Carolina brought this original action
against the State of North Carolina, seeking an equitable
apportionment of the Catawba River. We appointed a
Special Master and referred the matter to her, together
with the motions of three nonstate entities seeking to
intervene in the dispute as parties. South Carolina op­
posed the motions. After holding a hearing, the Special
Master granted the motions and, upon South Carolina’s
request, memorialized the reasons for her decision in a
First Interim Report. South Carolina then presented
exceptions, and we set the matter for argument.
   Two of the three proposed intervenors have satisfied the
standard for intervention in original actions that we ar­
ticulated nearly 60 years ago in New Jersey v. New York,
345 U. S. 369 (1953) (per curiam). Accordingly, we over­
rule South Carolina’s exceptions with respect to the Ca­
tawba River Water Supply Project (hereinafter CRWSP)
and Duke Energy Carolinas, LLC (hereinafter Duke En­
ergy), but we sustain South Carolina’s exception with
respect to the city of Charlotte, North Carolina (hereinaf­
ter Charlotte).
2          SOUTH CAROLINA v. NORTH CAROLINA

                     Opinion of the Court

                             I

                             A

   We granted leave for South Carolina to file its complaint
in this matter two years ago. South Carolina v. North
Carolina, 552 U. S. 804 (2007). The gravamen of the
complaint is that North Carolina has authorized upstream
transfers of water from the Catawba River basin that
exceed North Carolina’s equitable share of the river. It
has done so, according to the complaint, pursuant to a
North Carolina statute that requires any person seeking
to transfer more than 2 million gallons of water per day
(mgd) from the Catawba River basin to obtain a permit
from the North Carolina Environmental Management
Commission.        See N. C. Gen. Stat. Ann. §143–
215.22L(a)(1) (Lexis 2007); §143–215.22G(1)(h). Through
that agency, the complaint alleges, North Carolina has
issued at least two such permits, one to Charlotte for the
transfer of up to 33 mgd, and one to the North Carolina
cities of Concord and Kannapolis for the transfer of 10
mgd. In addition, the complaint alleges, North Carolina’s
permitting statute “grandfathers” a 5 mgd transfer by the
CRWSP, and “implicitly authorize[s]” an unknown number
of transfers of less than 2 mgd. Complaint ¶¶18, 21, 22.
South Carolina claims that the net effect of these up­
stream transfers is to deprive South Carolina of its equi­
table share of the Catawba River’s water, particularly
during periods of drought or low river flow.
   South Carolina seeks relief in the form of a decree that
equitably apportions the Catawba River between the two
States, enjoins North Carolina from authorizing transfers
of water from the Catawba River exceeding that State’s
equitable share, and declares North Carolina’s permitting
statute invalid to the extent it is used to authorize trans­
fers of water from the Catawba River that exceed North
Carolina’s equitable share. See generally Complaint,
Prayer for Relief ¶¶1–3. The complaint does not specify a
                  Cite as: 558 U. S. ____ (2010)             3

                      Opinion of the Court

minimum flow of water that would satisfy South Caro­
lina’s equitable needs, but it does offer a point of reference.
In a recent “multi-stakeholder negotiation process” involv­
ing the Federal Energy Regulatory Commission (hereinaf­
ter FERC), Duke Energy, and various groups from both
States, it was agreed, according to the complaint, that
South Carolina should receive from the Catawba River a
continuous flow of water of no less than 1,100 cubic feet
per second, or about 711 mgd. Complaint ¶14.
   This negotiated figure may prove unattainable. Accord­
ing to the complaint, natural conditions and periodic
fluctuations have caused the Catawba River’s flow to fall
below 1,100 cubic feet per second. Duke Energy, which
generates hydroelectric power from a series of reservoirs
on the Catawba River, developed a model to estimate the
river’s flow if the river were not impounded. Id., ¶¶8, 16.
The complaint notes that according to Duke Energy’s
model, the Catawba River—even in its natural state—
often would not deliver into South Carolina a minimum
average daily flow of 1,100 cubic feet per second. Id., ¶16;
App. to Motion of State of South Carolina for Leave to File
Complaint, Complaint, and Brief in Support of its Motion
for Leave to File Complaint 18. South Carolina contends
that North Carolina’s authorization of large transfers of
water from the Catawba River basin has exacerbated
these conditions.
   Shortly after we granted leave to file the complaint, two
of the entities named in the complaint—the CRWSP and
Duke Energy—filed motions for leave to intervene as
parties. The CRWSP sought leave to intervene as a party­
defendant, asserting its interest as a “riparian user of the
Catawba River” and claiming that this interest was not
adequately represented because of the CRWSP’s “inter­
state nature.” Motion of Catawba River Water Supply
Project for Leave to Intervene and Brief in Support of
Motion 8, 9. Specifically, the CRWSP noted that it is a
4            SOUTH CAROLINA v. NORTH CAROLINA

                        Opinion of the Court

bistate entity that is jointly owned and regulated by, and
supplies water to, North Carolina’s Union County and
South Carolina’s Lancaster County. Id., at 9. Duke En­
ergy sought leave to intervene and file an answer, assert­
ing an interest as the operator of 11 dams and reservoirs
on the Catawba River that control the river’s flow, as the
holder of a 50-year license1 governing Duke Energy’s
hydroelectric power operations, and as the entity that
orchestrated the multistakeholder negotiation process
culminating in a Comprehensive Relicensing Agreement
(CRA) signed by 70 entities from both States in 2006.
Duke Energy Carolinas, LLC’s Motion and Brief in Sup­
port of Motion to Intervene and File Answer, and Answer
2, 5. This CRA set forth the terms under which Duke
Energy has applied to renew its FERC license, id., at 5,
and Duke Energy asserted that neither State would repre­
sent its “particular amalgam of federal, state and private
interests,” id., at 14. South Carolina opposed both mo­
tions, and we referred them to the Special Master. 552
U. S. 1160 (2008).
   One month later, a third entity named in the complaint,
the city of Charlotte, also sought leave to intervene as a
party-defendant. In its brief, Charlotte asserted an inter­
est, both as the holder of a permit authorizing the transfer
of 33 mgd from the Catawba River basin—the largest
single transfer identified in the complaint—and as the
potential source of the 10 mgd transfer approved for the
cities of Concord and Kannapolis. Motion for Leave to
Intervene of City of Charlotte, North Carolina, and Brief
in Support of Motion 5, 7.2 Charlotte argued that North
——————
  1 The license was issued in 1958 to Duke Energy’s predecessor by the

Federal Power Commission, a predecessor of the FERC. For conven­
ience, we will refer to Duke Energy’s “FERC license” herein.
  2 Charlotte also asserted an interest in protecting the terms of the

CRA, to which Charlotte was a signatory but to which North Carolina,
which has conflicting duties under §401 of the Clean Water Act, 86
                    Cite as: 558 U. S. ____ (2010)                 5

                        Opinion of the Court

Carolina could not represent the city’s interests effectively
because the State was duty bound to represent the inter­
ests of all North Carolina users of the Catawba River’s
water, including users whose interests were not aligned
with Charlotte’s. Id., at 17. South Carolina also opposed
Charlotte’s motion, and we referred it to the Special Mas­
ter. 552 U. S. 1254 (2008).
                             B
   The Special Master held a hearing and issued an order
granting all three motions for leave to intervene. At South
Carolina’s request, the Special Master set forth her find­
ings and decision as a First Interim Report, and it is this
Report to which South Carolina now presents exceptions.
   The Special Master recognized that this Court has
exercised jurisdiction over nonstate parties in original
actions between two or more States. She also recognized
that in New Jersey v. New York, 345 U. S. 369, the Court
considered the “appropriate standard” for a nonstate
entity’s motion to intervene in an original action. First
Interim Report of Special Master, O. T. 2008, No. 138,
Orig., p. 12 (First Interim Rept.). But in attempting to
give context to our standard, she looked beyond interven­
tion and considered original actions in which the Court
has allowed nonstate entities to be named as defendants
by the complaining State. From those examples, the
Special Master “distilled the following rule” governing
motions to intervene in original actions by nonstate
entities:
     “Although the Court’s original jurisdiction presump­
     tively is reserved for disputes between sovereign
——————
Stat. 877, as added, 33 U. S. C. §1341, was not. North Carolina op­
posed this argument, and the Special Master did not rely on it in
recommending that Charlotte’s motion to intervene should be granted.
As Charlotte does not reassert this argument here, we do not consider
it.
6           SOUTH CAROLINA v. NORTH CAROLINA

                      Opinion of the Court

    states over sovereign matters, nonstate entities may
    become parties to such original disputes in appropri­
    ate and compelling circumstances, such as where the
    nonstate entity is the instrumentality authorized to
    carry out the wrongful conduct or injury for which the
    complaining state seeks relief, where the nonstate en­
    tity has an independent property interest that is di­
    rectly implicated by the original dispute or is a sub­
    stantial factor in the dispute, where the nonstate
    entity otherwise has a ‘direct stake’ in the outcome of
    the action within the meaning of the Court’s cases
    discussed above, or where, together with one or more
    of the above circumstances, the presence of the non­
    state entity would advance the ‘full exposition’ of the
    issues.” Id., at 20–21.
  Applying this broad rule, the Special Master found that
each proposed intervenor had a sufficiently compelling
interest to justify intervention. The Special Master re­
jected South Carolina’s proposal to limit intervention to
the remedy phase of this litigation and recommended that
this Court grant the motions to intervene.
                              II 

                              A

   Participation by nonstate parties in actions arising
under our original jurisdiction is not a new development.
Article III, §2, of the Constitution expressly contemplates
suits “between a State and Citizens of another State” as
falling within our original jurisdiction, see, e.g., Georgia v.
Brailsford, 2 Dall. 402 (1792), and for more than two
centuries the Court has exercised that jurisdiction over
nonstate parties in suits between two or more States, see
New York v. Connecticut, 4 Dall. 1 (1799); Missouri v.
Illinois, 180 U. S. 208, 224–225 (1901). Nonstate entities
have even participated as parties in disputes between
States, such as the one before us now, where the States
                      Cite as: 558 U. S. ____ (2010)                        7

                           Opinion of the Court

were seeking equitable apportionment of water resources.
See, e.g., Arizona v. California, 460 U. S. 605, 608, n. 1
(1983); Texas v. New Mexico, 343 U. S. 932 (1952); New
Jersey v. City of New York, 279 U. S. 823 (1929) (per cu
riam). It is, thus, not a novel proposition to accord party
status to a citizen in an original action between States.
  This Court likewise has granted leave, under appropri­
ate circumstances, for nonstate entities to intervene as
parties in original actions between States for nearly 90
years. See Maryland v. Louisiana, 451 U. S. 725, 745,
n. 21 (1981). In Oklahoma v. Texas, 258 U. S. 574, 581,
598 (1922), a boundary dispute that threatened to erupt in
armed hostilities, the Court allowed individual and corpo­
rate citizens to intervene to protect their rights in con­
tested land. See, e.g., Oklahoma v. Texas, 254 U. S. 609
(1920).3 More recently, the Court has allowed a munici­
pality to intervene in a sovereign boundary dispute, see
Texas v. Louisiana, 426 U. S. 465, 466 (1976) (per curiam),
and has permitted private corporations to intervene in an
original action challenging a State’s imposition of a tax
that burdened interstate commerce and contravened the
Supremacy Clause, see Maryland v. Louisiana, supra, at
745, n. 21.
  In this case, the Special Master crafted a rule of inter­
vention that accounts for the full compass of our prece­
dents. But a compelling reason for allowing citizens to
participate in one original action is not necessarily a com­
pelling reason for allowing citizens to intervene in all
——————
  3 THE  CHIEF JUSTICE argues against drawing conclusions from the
intervention that we allowed in Oklahoma v. Texas, 254 U. S. 609
(1920). See post, at 7–8 (opinion concurring in judgment in part and
dissenting in part). But the circumstances surrounding that dispute fit
the “ ‘model case’ ” for invoking this Court’s original jurisdiction, post, at
2, and counsel against inferring from our precedents, as THE CHIEF
JUSTICE does with respect to equitable apportionment actions, a rule
against nonstate intervention in such “weighty controversies,” ibid.
8             SOUTH CAROLINA v. NORTH CAROLINA

                          Opinion of the Court

original actions. We therefore decline to adopt the Special
Master’s proposed rule. As the Special Master acknowl­
edged, the Court in New Jersey v. New York, supra, set
down the “appropriate standard” for intervention in origi­
nal actions by nonstate entities. First Interim Rept. 12.
We believe the standard that we applied in that case
applies equally well here.4
  In 1929, the State of New Jersey sued the State of New
York and city of New York for their diversion of the Dela­
ware River’s headwaters. 345 U. S., at 370. The Court
granted the Commonwealth of Pennsylvania leave to
intervene, and in 1931, entered a decree enjoining certain
diversions 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 Pennsyl­
vania filed oppositions. After the Court referred the mat­
ter to a special 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.
Pennsylvania had intervened pro interesse suo “to protect
the rights and interests of Philadelphia and Eastern
Pennsylvania in the Delaware River.” Id., at 374; see also
New Jersey v. New York, 283 U. S. 336, 342 (1931). In
view of Pennsylvania’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–
——————
  4 Accordingly, we need not decide South Carolina’s first exception to

the Special Master’s conclusion that intervention is proper “whenever
the movant is the ‘instrumentality’ authorized to engage in conduct
alleged to harm the plaintiff State, has an ‘independent property
interest’ at issue in the action, or otherwise has a ‘direct stake’ in the
outcome of the action.” Exceptions of State of South Carolina to First
Interim Report of Special Master and Brief in Support of Exceptions i.
                 Cite as: 558 U. S. ____ (2010)            9

                     Opinion of the Court

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 admini­
stration.” 345 U. S., at 373. The Court, thus, set forth the
following standard governing intervention 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).
   We acknowledge that the standard for intervention in
original actions by nonstate entities is high—and appro­
priately so. Such actions tax the limited resources of this
Court by requiring us “awkwardly to play the role of fact­
finder” and diverting our attention from our “primary
responsibility as an appellate tribunal.” Ohio v. Wyan
dotte Chemicals Corp., 401 U. S. 493, 498 (1971); Mary
land v. Louisiana, 451 U. S. 725, 762 (1981) (Rehnquist,
J., dissenting). In order to ensure that original actions do
not assume the “dimensions of ordinary class actions,”
New Jersey v. New York, 345 U. S., at 373, we exercise our
original jurisdiction “sparingly” and retain “substantial
discretion” to decide whether a particular claim requires
“an original forum in this Court,” Mississippi v. Louisiana,
506 U. S. 73, 76 (1992) (internal quotation marks omitted).
   Respect for state sovereignty also calls for a high
threshold to intervention by nonstate parties in a sover­
eign dispute committed to this Court’s original jurisdic­
10           SOUTH CAROLINA v. NORTH CAROLINA

                         Opinion of the Court

tion. Under 28 U. S. C. §1251, this Court exercises “origi­
nal and exclusive” jurisdiction to resolve controversies
between States that, if arising among independent na­
tions, “would be settled by treaty or by force.” Kansas v.
Colorado, 206 U. S. 46, 98 (1907). This Court has de­
scribed its original jurisdiction as “delicate and grave,”
Louisiana v. Texas, 176 U. S. 1, 15 (1900), and has
guarded against its use as a forum in which “a state might
be judicially impeached on matters of policy by its own
subjects,” New Jersey v. New York, 345 U. S., at 373. In
its sovereign capacity, a State represents the interests of
its citizens in an original action, the disposition of which
binds the citizens. Nebraska v. Wyoming, supra, at 22;
New Jersey v. New York, 345 U. S., at 372–373. A respect
for sovereign dignity, therefore, counsels in favor of re­
straint in allowing nonstate entities to intervene in such
disputes. See ibid.; accord, United States v. Texas, 143
U. S. 621, 643 (1892) (“[E]xclusive jurisdiction was given
to this court, because it best comported with the dignity of
a State, that a case in which it was a party should be
determined in the highest, rather than in a subordinate
judicial tribunal of the nation”).5
   That the standard for intervention in original actions by
nonstate entities is high, however, does not mean that it is
insurmountable. Indeed, as the Special Master correctly
recognized, our practice long has been to allow such inter­
vention in compelling circumstances. See Oklahoma v.

——————
   5 South Carolina has not invoked the Eleventh Amendment as a basis

for opposing intervention. It has noted, however, that the proposed
intervenors’ claims are, in effect, against South Carolina, and thus has
reserved the right to argue that the Eleventh Amendment bars particu­
lar forms of relief sought by the proposed intervenors. As in New Jersey
v. New York, 345 U. S. 369, 372 (1953) (per curiam), we express no view
whether the Eleventh Amendment is implicated where a nonstate
entity seeks to intervene as a defendant in an original action over a
State’s objection.
                 Cite as: 558 U. S. ____ (2010)          11

                     Opinion of the Court

Texas, 258 U. S., at 581. Over the “strong objections” of
three States, for example, the Court allowed Indian tribes
to intervene in a sovereign dispute concerning the equita­
ble apportionment of the Colorado River. Arizona v. Cali
fornia, 460 U. S., at 613. The Court did so notwithstand­
ing the Tribes’ simultaneous representation by the United
States. Id., at 608–609, 612. And in a boundary dispute
among Texas, Louisiana, and the United States, the Court
allowed the city of Port Arthur, Texas, to intervene for the
purpose of protecting its interests in islands in which the
United States claimed title. Texas v. Louisiana, 426 U. S.,
at 466; Texas v. Louisiana, 416 U. S. 965 (1974). In both
of these examples, the Court found compelling interests
that warranted allowing nonstate entities to intervene in
original actions in which the intervenors were nominally
represented by sovereign parties.
                             B
                             1
  Applying the standard of New Jersey v. New York, su
pra, here, we conclude that the CRWSP has demonstrated
a sufficiently compelling interest that is unlike the inter­
ests of other citizens of the States. The CRWSP is an
unusual municipal entity, established as a joint venture
with the encouragement of regulatory authorities in both
States and designed to serve the increasing water needs of
Union County, North Carolina, and Lancaster County,
South Carolina. It has an advisory board consisting of
representatives from both counties, draws its revenues
from its bistate sales, and operates infrastructure and
assets that are owned by both counties as tenants-in­
common. We are told that approximately 100,000 indi­
viduals in each State receive their water from the CRWSP
and that “roughly half” of the CRWSP’s total withdrawals
of water from the Catawba River go to South Carolina
consumers. Reply of Catawba River Water Supply Project
12         SOUTH CAROLINA v. NORTH CAROLINA

                     Opinion of the Court

to Exceptions of South Carolina to First Interim Report of
Special Master 22 (hereinafter CRWSP Reply). It is diffi­
cult to conceive of a more purely bistate entity.
  In addition, the CRWSP relies upon authority granted
by both States to draw water from the Catawba River and
transfer that water from the Catawba River basin. The
CRWSP draws all of its water from an intake located
below the Lake Wylie dam in South Carolina. South
Carolina licensed the CRWSP to withdraw a total of 100
mgd from the Catawba River and issued a certificate to
the CRWSP in 1989 authorizing up to 20 mgd to be trans­
ferred out of the Catawba River basin. Id., at 6–7; Answer
to Bill of Complaint ¶21. Lancaster County currently uses
approximately 2 mgd of this amount, Union County uses
approximately 5 mgd, and the remaining 13 mgd are not
used at this time. CRWSP Reply 7. The CRWSP pumps
Union County’s allocation across the state border pursu­
ant to a parallel certificate issued by North Carolina
authorizing a 5 mgd transfer, ibid., and the complaint
specifically identifies this transfer as contributing to
South Carolina’s harm, Complaint ¶21.             Thus, the
CRWSP’s activities depend upon authority conferred by
both States.
  On these facts, we think it is clear that the CRWSP has
carried its burden of showing a compelling interest in the
outcome of this litigation that distinguishes the CRWSP
from all other citizens of the party States. See New Jersey
v. New York, supra, at 373. Apart from its interest as a
user of the Catawba River’s water, the CRWSP has made
a $30 million investment in its plant and infrastructure,
with each participating county incurring approximately
half of this cost as debt. Each county is responsible for
one-half of the CRWSP’s cost of operations, and the ven­
ture is designed to break even from year to year. Any
disruption to the CRWSP’s operations would increase—not
lessen—the difficulty of our task in achieving a “just and
                    Cite as: 558 U. S. ____ (2010)                  13

                         Opinion of the Court

equitable” allocation in this dispute. See Nebraska v.
Wyoming, 325 U. S. 589, 618 (1945). We believe that the
CRWSP has shown a compelling interest in protecting the
viability of its operations, which are premised on a fine
balance between the joint venture’s two participating
counties.
   We are further persuaded that neither State can prop­
erly represent the interests of the CRWSP in this litiga­
tion. See New Jersey v. New York, 345 U. S., at 373. The
complaint attributes a portion of the total water transfers
that have harmed South Carolina to the CRWSP, yet
North Carolina expressly states that it “cannot represent
the interests of the joint venture.” Tr. of Oral Arg. 54. A
moment’s reflection reveals why this is so. In this dispute,
as in all disputes over limited resources, each State maxi­
mizes its equitable share of the Catawba River’s water
only by arguing that the other State’s equitable share
must be reduced. See, e.g., Colorado v. New Mexico, 459
U. S. 176, 186–187 (1982). It is thus likely that North
Carolina, in response to South Carolina’s demand for a
greater share of the Catawba River’s water, will take the
position that downstream users—such as Lancaster
County6—should receive less water. See Tr. of Oral Arg.
52 (“From North Carolina’s perspective, South Carolina is
receiving much more water under this negotiated agree­
ment than they could ever hope to achieve in an equitable
apportionment action”). The stresses that this litigation
would place upon the CRWSP threaten to upset the fine
balance on which the joint venture is premised, and nei­
——————
  6 As a further complication, we are told, Lancaster County has an

obligation to provide water service to certain customers in Mecklenburg
County, North Carolina. CRWSP Reply 6. Thus, South Carolina may
not be interested in protecting all uses of Lancaster County’s share of
the CRWSP’s water. This additional intermingling of state interests
further supports our conclusion that neither State adequately repre­
sents the CRWSP’s inherently bistate interests.
14          SOUTH CAROLINA v. NORTH CAROLINA

                      Opinion of the Court

ther State has sufficient interest in maintaining that
balance to represent the full scope of the CRWSP’s
interests.
  Accordingly, we believe that the CRWSP should be
allowed to intervene to represent its own compelling inter­
ests in this litigation. We thus overrule South Carolina’s
exception.
                               2
   We conclude, as well, that Duke Energy has demon­
strated powerful interests that likely will shape the out­
come of this litigation. To place these interests in context,
it is instructive to consider the “flexible” process by which
we arrive at a “ ‘just and equitable apportionment’ ” of an
interstate stream. Colorado v. New Mexico, supra, at 183.
We do not approach the task in formulaic fashion, New
Jersey v. New York, 283 U. S., at 343, but we consider “all
relevant factors,” including, but not limited to:
     “ ‘physical and climatic conditions, the consumptive
     use of water in the several sections of the river, the
     character and rate of return flows, the extent of estab­
     lished uses, the availability of storage water, the prac­
     tical effect of wasteful uses on downstream areas,
     [and] the damage to upstream areas as compared to
     the benefits to downstream areas if a limitation is im­
     posed on the former.’ ” Colorado v. New Mexico, su
     pra, at 183 (quoting Nebraska v. Wyoming, supra, at
     618).
In performing this task, there is no substitute for “ ‘the
exercise of an informed judgment,’ ” Colorado v. New
Mexico, supra, at 183, and we will not hesitate to seek out
the most relevant information from the source best situ­
ated to provide it. See Maryland v. Louisiana, 451 U. S.,
at 745, n. 21 (allowing intervention of private pipeline
companies “in the interest of a full exposition of the
                   Cite as: 558 U. S. ____ (2010)               15

                       Opinion of the Court

issues”).
   With these considerations in mind, we turn to Duke
Energy’s asserted interests. Duke Energy operates 11
dams and reservoirs in both States that generate electric­
ity for the region and control the flow of the river. The
complaint itself acknowledges the relationship between
river flow and Duke Energy’s operations, noting that a
severe drought that ended in 2002 forced Duke Energy to
“reduce dramatically” its hydroelectric power generation
from the Catawba River. Complaint ¶17(c). It is likely
that any equitable apportionment of the river will need to
take into account the amount of water that Duke Energy
needs to sustain its operations and provide electricity to
the region, thus giving Duke Energy a strong interest in
the outcome of this litigation. See Colorado v. New Mex
ico, supra, at 188 (noting the appropriateness of consider­
ing “the balance of harm and benefit that might result”
from a State’s proposed diversion of a river). There is,
moreover, no other similarly situated entity on the Ca­
tawba River, setting Duke’s interests apart from the class
of all other citizens of the States. See New Jersey v. New
York, supra, at 373.
   Just as important, Duke Energy has a unique and com­
pelling interest in protecting the terms of its existing
FERC license and the CRA that forms the basis of Duke
Energy’s pending renewal application.7 Through its dams,
Duke Energy controls the flow of the Catawba River under
the terms of its 50-year FERC license, which regulates the
very subject matter in dispute: the river’s minimum flow
into South Carolina. See Order Issuing License (Major),
Duke Power Co., Project No. 2232, 20 F. P. C. 360, 371–372
(1958) (Articles 31 and 32). The CRA, likewise, represents
——————
  7 Duke Energy is operating under a temporary extension of its 50­

year FERC license, which expired in 2008, and the CRA represents
Duke Energy’s investment in a new 50-year license.
16         SOUTH CAROLINA v. NORTH CAROLINA

                     Opinion of the Court

the full consensus of 70 parties from both States regarding
the appropriate minimum continuous flow of Catawba
River water into South Carolina under a variety of natural
conditions and, in times of drought, the conservation
measures to be taken by entities that withdraw water
from the Catawba River. These factors undeniably are
relevant to any “just and equitable apportionment” of the
Catawba River, see Colorado v. New Mexico, 459 U. S., at
183, and we are likely to consider them in reaching our
ultimate disposition of this case. Thus, we find that Duke
Energy has carried its burden of showing unique and
compelling interests.
   We also have little difficulty in concluding that neither
State sufficiently represents these compelling interests.
Neither State has signed the CRA or expressed an inten­
tion to defend its terms. To the contrary, North Carolina
has expressed an intention to seek its modification. Tr. of
Oral Arg. 51–52. Given the importance of Duke Energy’s
interests and their relevance to our ultimate decision, we
believe these interests should be represented by a party in
this action, and we find that neither State is situated to do
so properly. We believe that Duke Energy should be
permitted to represent its own interests.
   For these reasons, we agree with the Special Master
that Duke Energy should be permitted to intervene, and
we overrule South Carolina’s exception in that regard.
                             3
  We conclude, however, that Charlotte has not carried its
burden of showing a sufficient interest for intervention in
this action. Charlotte is a municipality of North Carolina,
and for purposes of this litigation, its transfers of water
from the Catawba River basin constitute part of North
Carolina’s equitable share. While it is true that the com­
plaint names Charlotte as an entity authorized by North
Carolina to carry out a large transfer of water from the
                  Cite as: 558 U. S. ____ (2010)            17

                      Opinion of the Court

Catawba River basin, the complaint does not seek relief
against Charlotte directly. Rather, the complaint seeks
relief against all North Carolina-authorized transfers of
water from the Catawba River basin, “past or future,” in
excess of North Carolina’s equitable share. Complaint,
Prayer for Relief ¶2. Charlotte, therefore, occupies a class
of affected North Carolina users of water, and the magni­
tude of Charlotte’s authorized transfer does not distin­
guish it in kind from other members of the class. See New
Jersey v. New York, 345 U. S., at 373, and n. (noting that
Philadelphia represented half of the Pennsylvania’s citi­
zens in the watershed). Nor does Charlotte represent
interstate interests that fall on both sides of this dispute,
as the CRWSP does, such that the viability of Charlotte’s
operations in the face of this litigation is called into ques­
tion. Its interest is solely as a user of North Carolina’s
share of the Catawba River’s water.
   Charlotte’s interest falls squarely within the category of
interests with respect to which a State must be deemed to
represent all of its citizens. As we recognized in New
Jersey v. New York, a State’s sovereign interest in ensur­
ing an equitable share of an interstate river’s water is
precisely the type of interest that the State, as parens
patrie, represents on behalf of its citizens. See also United
States v. Nevada, 412 U. S., at 539; Nebraska v. Wyoming,
325 U. S., at 616. That is why, in New Jersey v. New York,
supra, we required that a proposed intervenor show a
compelling interest “in his own right,” distinct from the
collective interest of “all other citizens and creatures of the
state,” whose interest the State presumptively represents
in matters of sovereign policy. Id., at 373. We conclude
that Charlotte has not carried that burden. Thus, respect
for “sovereign dignity” requires us to recognize that North
Carolina properly represents Charlotte in this dispute
over a matter of uniquely sovereign interest. See ibid.
   North Carolina’s own statements only reinforce this
18            SOUTH CAROLINA v. NORTH CAROLINA

                          Opinion of the Court

conclusion. North Carolina has said that it will defend
Charlotte’s authorized 33 mgd transfer. Tr. of Oral Arg.
52–53. The State expressly disagrees with Charlotte’s
assertion that the city’s interest is not adequately repre­
sented by the State. Brief of State of North Carolina in
Opposition to Plaintiff’s Exceptions 22. Indeed, in re­
sponse to Charlotte’s motion to intervene, North Carolina
wrote the following:
     “[T]he State must represent the interests of every per­
     son that uses water from the North Carolina portion
     of the Catawba River basin. In fact, the State has a
     particular concern for its political subdivisions, such
     as Charlotte, which actually operate the infrastruc­
     ture to provide water to the State’s citizens. . . . The
     State has every reason to defend the [transfers] that it
     has authorized for the benefit of its citizens. The
     State cannot agree with any implication that because
     it represents all of the users of water in North Caro­
     lina it cannot, or will not represent the interests of
     Charlotte in this litigation initiated by South Caro­
     lina.” Brief for State of North Carolina in Response to
     City of Charlotte’s Motion for Leave to Intervene and
     File Answer 1–2.
These statements are consistent with North Carolina’s
role as parens patriae, and we see no reason that North
Carolina cannot represent Charlotte’s interest in this
sovereign dispute. See New Jersey v. New York, supra, at
374 (noting that Philadelphia’s interest “is invariably
served by the Commonwealth’s position”).
  Because we are not persuaded that Charlotte’s interest
is sufficiently unique and not properly represented by
North Carolina to require the city’s intervention as a party
in this litigation, we sustain South Carolina’s exception.8
——————
 8 Federal   Rule of Civil Procedure 24 does not require a contrary re­
                     Cite as: 558 U. S. ____ (2010)                  19

                         Opinion of the Court

                             III
   We thus overrule South Carolina’s exceptions to the
Special Master’s First Interim Report with respect to the
CRWSP and Duke Energy, but we sustain South Caro­
lina’s exception with respect to Charlotte.
                                            It is so ordered.




——————
sult. This Court’s Rule 17.2 allows the Federal Rules of Civil Procedure
to be taken as “guides” to procedure in original actions. See Arizona v.
California, 460 U. S. 605, 614 (1983). Even if we were to look to the
standard for intervention of right in civil matters, Charlotte would not
be entitled to intervene in this dispute because an existing party—
North Carolina—adequately represents Charlotte’s interest. See Fed.
Rule Civ. Proc. 24(a)(2). To the extent that the standard for permissive
intervention may be an appropriate guide when a movant presents a
sufficiently “important but ancillary concern,” see Arizona, supra, at
614–616, we find no such concern here. North Carolina’s adequate
representation of Charlotte and the heightened standard for interven­
tion in original actions, see New Jersey v. New York, 345 U. S., at 373,
persuade us not to apply the standard for permissive intervention set
forth in Federal Rule of Civil Procedure 24(b)(1)(B).
                 Cite as: 558 U. S. ____ (2010)           1

                   Opinion of ROBERTS, C. J.

SUPREME COURT OF THE UNITED STATES
                         _________________

                        No. 138, Orig.
                         _________________


 STATE OF SOUTH CAROLINA, PLAINTIFF v. STATE 

             OF NORTH CAROLINA 

 ON EXCEPTIONS TO THE REPORT OF THE SPECIAL MASTER
                      [January 20, 2010]

  CHIEF JUSTICE ROBERTS, with whom JUSTICE THOMAS,
JUSTICE GINSBURG, and JUSTICE SOTOMAYOR join, concur
ring in the judgment in part and dissenting in part.
  The Court correctly rejects the Special Master’s formu
lation of a new test for intervention in original actions,
and correctly denies the city of Charlotte leave to inter
vene. The majority goes on, however, to misapply our
established test in granting intervention to Duke Energy
Carolinas, LLC (Duke Energy), and the Catawba River
Water Supply Project (CRWSP).
  The result is literally unprecedented: Even though
equitable apportionment actions are a significant part of
our original 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 apportionment of an interstate waterway is a
sovereign dispute, and the key to intervention in such an
action is just that—sovereignty. The Court’s decision to
permit nonsovereigns 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 between sovereigns into a forum
for airing private interests. Given the importance of
maintaining the proper limits on that jurisdiction, I re
spectfully dissent.
2           SOUTH CAROLINA v. NORTH CAROLINA

                    Opinion of ROBERTS, C. J.

                                I
   Two basic principles have guided the exercise of our
constitutionally 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
accordingly focus on “the nature of the interest of the
complaining State,” and in particular the “seriousness and
dignity” 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 U. S. 1, 8–9 (2001); Pennsylvania v. New Jersey, 426
U. S. 660, 665 (1976) (per curiam) (It is “settled doctrine
that a State has standing to sue only when its sovereign or
quasi-sovereign interests are implicated and it is not
merely litigating as a volunteer the personal claims of its
citizens”). And in deciding whether a State meets that
requirement, this Court considers whether the State is “in
full control of [the] litigation.” Kansas v. Colorado, supra,
at 8.
   The second guiding principle is a practical one: We are
not well suited to assume the role of a trial judge. See
Ohio v. Wyandotte Chemicals Corp., 401 U. S. 493, 498
(1971). We have attempted to address that reality by
relying on the services of able special masters, who have
become vitally important in allowing us to manage our
                  Cite as: 558 U. S. ____ (2010)            3

                    Opinion of ROBERTS, C. J.

original docket. But the responsibility for the exercise of
this Court’s original jurisdiction remains ours alone under
the Constitution.
   These two considerations—that our original jurisdiction
is limited to high claims affecting state sovereignty, and
that practical realities limit our ability to act as a trial
court—converge in our standard for intervention in origi
nal actions. We articulated that standard in New Jersey v.
New York, 345 U. S. 369, 373 (1953) (per curiam). There,
we denied the city of Philadelphia’s motion for leave to
intervene in an action, to which the Commonwealth of
Pennsylvania was already a party, involving the appor
tionment of the Delaware River. Id., at 373–374. We set
out the following test for intervention in an original action:
“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.” Id., at 373.
   This exacting standard is grounded on a “necessary
recognition of sovereign dignity,” id., at 373, under which
“the state, when a party to a suit involving a matter of
sovereign interest, ‘must be deemed to represent all its
citizens,’ ” id., at 372 (quoting Kentucky v. Indiana, 281
U. S. 163, 173–174 (1930)). In applying that doctrine to
motions to intervene, the New Jersey v. New York test
precludes a State from being “judicially impeached on
matters of policy by its own subjects,” and prevents the
use of the Court’s original jurisdiction to air “intramural
dispute[s]” that should be settled in a different forum—
namely, within the States. 345 U. S., at 373.
   The New Jersey v. New York test is also “a working rule
for good judicial administration.” Ibid. Without it, “there
would be no practical limitation on the number of citizens,
as such, who would be entitled to be made parties.” Ibid.
Indeed, the Court observed that allowing Philadelphia to
4          SOUTH CAROLINA v. NORTH CAROLINA

                   Opinion of ROBERTS, C. J.

intervene would have made it difficult to refuse attempts
to intervene by other users of water from the Delaware
River, including other cities, and even “[l]arge industrial
plants.” Ibid. The New Jersey v. New York test, properly
applied, provides a much-needed limiting principle that
prevents the expansion of our original proceedings “to the
dimensions of ordinary class actions,” ibid., or “town
meeting lawsuits,” id., at 376 (Jackson, J., dissenting).
See also Ohio v. Wyandotte Chemicals Corp., supra, at
504; Utah v. United States, 394 U. S. 89, 95–96 (1969) (per
curiam).
                              II
  Applying these principles, this Court has never granted
a nonsovereign entity’s motion to intervene in an equitable
apportionment action. The reason is straightforward: An
interest in water is an interest shared with other citizens,
and is properly pressed or defended by the State. And a
private entity’s interest in its particular share of the
State’s water, once the water is allocated between the
States, is an “intramural dispute” to be decided by each
State on its own. New Jersey v. New York, supra, at 373.
  The interests of a State’s citizens in the use of water
derive entirely from the State’s sovereign interest in the
waterway. If the State has no claim to the waters of an
interstate river, then its citizens have none either. See
Hinderlider v. La Plata River & Cherry Creek Ditch Co.,
304 U. S. 92, 102 (1938). We have long recognized, there
fore, that the State must be deemed to represent its citi
zens’ interests in an equitable apportionment action. See
United States v. Nevada, 412 U. S. 534, 539 (1973) (per
curiam) (“For the purposes of dividing the waters of an
interstate stream with another State, [a State] has the
right, parens patriae, to represent all the nonfederal users
in its own State insofar as the share allocated to the other
State is concerned”). Precisely because the State repre
                 Cite as: 558 U. S. ____ (2010)            5

                   Opinion of ROBERTS, C. J.

sents all its citizens in an equitable apportionment action,
these citizens have no claim themselves against the other
State. They are instead “bound by the result reached
through representation by their respective States,” regard
less of whether those citizens are parties to the suit.
Nebraska v. Wyoming, 515 U. S. 1, 22 (1995).
   This basic principle applies without regard to whether
the State agrees with and will advance the particular
interest asserted by a specific private entity. The State
“ ‘must be deemed to represent all its citizens,’ ” New Jer
sey v. New York, supra, at 372 (quoting Kentucky v. Indi
ana, supra, at 173–174; emphasis added), not just those
who subscribe to the State’s position before this Court.
The directive that a State cannot be “judicially impeached
on matters of policy by its own subjects,” New Jersey v.
New York, supra, at 373, obviously applies to the case in
which a subject disagrees with the position of the State.
   A State’s citizens also need not be made parties to an
equitable apportionment action because the Court’s judg
ment in such an action does not determine the water
rights of any individual citizen. We made that clear long
ago in two decisions arising from the same dispute, Wyo
ming v. Colorado, 298 U. S. 573 (1936), and Wyoming v.
Colorado, 309 U. S. 572 (1940). In those cases, Wyoming
sought to enforce this Court’s earlier decree apportioning
the Laramie River. See Wyoming v. Colorado, 260 U. S. 1
(1922). We held that the decree controlled the allocation
of water between Wyoming and Colorado, not within
them. As we recognized, our decision apportioning the
river did not “withdraw water claims dealt with therein
from the operation of local laws relating to their transfer
or . . . restrict their utilization in ways not affecting the
rights of one State and her claimants as against the other
State and her claimants.” 298 U. S., at 584. Thus, al
though the decree referred to particular uses of water in
Colorado, we held that those individual uses could vary
6            SOUTH CAROLINA v. NORTH CAROLINA

                       Opinion of ROBERTS, C. J.

from the terms set out in the decree, so long as the total
diversion of water in Colorado was no greater than the
decree allowed. See id., at 584–585; 309 U. S., at 579–581.
We reiterated the point in Nebraska v. Wyoming, 325 U. S.
589, 627 (1945), observing that the apportionment of a
waterway between the States has only an “indirect effect”
on the rights of individuals within the States.
   All this explains our long history of rejecting attempts
by nonsovereign entities to intervene in equitable appor
tionment actions. New Jersey v. New York was itself an
equitable apportionment suit, and we denied intervention
in that case. We have also summarily denied motions to
intervene in other water disputes between the States. See
Arizona v. California, 514 U. S. 1081 (1995); Arizona v.
California, 345 U. S. 914 (1953); Nebraska v. Wyoming,
296 U. S. 548 (1935); Wisconsin v. Illinois, 279 U. S. 821
(1929). And we have strongly intimated in other decisions
(albeit in dictum) that private entities can rarely, if ever,
intervene in original actions involving the apportionment
of interstate waterways. See United States v. Nevada,
supra, at 538 (“[I]ndividual users of water . . . ordinarily
would have no right to intervene in an original action in
this Court”); Nebraska v. Wyoming, 515 U. S., at 22 (“We
have said on many occasions that water disputes among
States may be resolved by compact or decree without the
participation of individual claimants”).1
——————
    1 Themajority contends that this dissent reads our precedents to
establish “a rule against nonstate intervention” in equitable appor
tionment actions. Ante, at 7, n. 3. The number of nonsovereigns that
the Court should permit to intervene in water disputes is small—
indeed, it was zero until today. But that does not mean that a private
entity could not satisfy the New Jersey v. New York test by, for exam
ple, asserting water-use rights that are not dependent upon the rights
of state parties. A private party (or perhaps a Compact Clause entity)
with a federal statutory right to a certain quantity of water might have
a compelling interest in an equitable apportionment action that is not
fairly represented by the States. The putative intervenors in this case,
                      Cite as: 558 U. S. ____ (2010)       7

                        Opinion of ROBERTS, C. J.

   The majority contends that the result in this case is not
a “new development,” and that its holding is supported by
“nearly 90 years” of precedent. Ante, at 6–7. But in sup
port of those statements, the majority cites only four
decisions in which the Court has granted a motion to
intervene in an original suit—and of course none in which
this Court granted the motion of a nonsovereign entity to
intervene in an equitable apportionment action. The cases
the majority cites demonstrate what constitutes a “compel
ling interest in [the intervenor’s] own right, apart from his
interest in a class with all other citizens and creatures of
the state.” New Jersey v. New York, supra, at 373. But
the intervenor interests in those cases were quite different
from the general shared interest in water at issue here.
   Take Arizona v. California, 460 U. S. 605 (1983). There
we allowed several Indian Tribes to intervene in a water
dispute. Id., at 615. As the Court in that case made clear,
however, the Indian Tribes were allowed to intervene
because they were sovereign entities. Ibid. The Court
distinguished New Jersey v. New York on that very
ground. See 460 U. S., at 615, n. 5.
   The other cases relied upon by the majority are even
farther afield. See Maryland v. Louisiana, 451 U. S. 725
(1981); Texas v. Louisiana, 426 U. S. 465 (1976) (per cu
riam); Oklahoma v. Texas, 258 U. S. 574 (1922). None was
an equitable apportionment action. Two involved bound
ary disputes in which the Court allowed nonsovereign
intervenors to claim title to certain parcels of property.
See Texas v. Louisiana, supra, at 466 (permitting inter
vention by the city of Port Arthur, Texas); Oklahoma v.
Texas, supra, at 580–581 (same for private parties). A
claim to title in a particular piece of property is quite
different from a general interest shared by all citizens in
the State’s waters. And it would be particularly inapt to
—————— 

however, do not hold rights of this sort. 

8          SOUTH CAROLINA v. NORTH CAROLINA

                   Opinion of ROBERTS, C. J.

draw general conclusions about intervention from Okla
homa v. Texas, in which the Court took the southern half
of the Red River into receivership. See 258 U. S., at 580.
In subsequently allowing persons to intervene to assert
claims to the subject property, the Court relied explicitly
on the fact that the receiver had possession and control of
the claimed parcels, and “no other court lawfully [could]
interfere with or disturb that possession or control.” Id.,
at 581.
  The majority’s reliance on Maryland v. Louisiana is
equally unavailing. There, several States challenged the
constitutionality of Louisiana’s application of a tax on
natural gas that was brought into that State. 451 U. S., at
728. In two sentences within a long footnote, the Court
mentioned that it was permitting a group of pipeline
companies to intervene and challenge the tax. Id., at 745,
n. 21. The Court made clear that the pipeline companies
were able to intervene in light of the particular circum
stances in that case—namely, Louisiana’s tax was “di
rectly imposed on the owner of imported gas,” and “the
pipelines most often own[ed] the gas.” Ibid. Again, an
interest in a tax imposed only on discrete parties is obvi
ously different from a general interest shared by all citi
zens of the State.
                             III
  Charlotte, Duke Energy, and CRWSP claim a variety of
specific needs for water to justify their intervention. But
all those particular needs derive from an interest in the
water of the Catawba River. That interest is not exclu
sive, but is instead shared “with all other citizens and
creatures of the state.” New Jersey v. New York, 345 U. S.,
at 373. The State’s “citizens and creatures” certainly put
the Catawba’s water and flow to different uses—many for
drinking water, some for farming or recreation, others for
generating power. That does not, however, make their
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                   Opinion of ROBERTS, C. J.

interest in the water itself unique. And it is the respective
interests of the States in the water itself that are being
litigated in this original action—not the claims of particu
lar citizens that they be allowed to put the water to speci
fied uses. The latter subject is “an intramural dispute
over the distribution of water within the [State],” ibid.,
and is not the subject of this original proceeding.
   The majority recognizes as much with respect to Char
lotte, ante, at 16–18, but departs from these principles in
granting intervention to Duke Energy and CRWSP. The
majority’s reasons for doing so do not withstand scrutiny.
   The majority initially contends that Duke Energy
should be allowed to intervene because it possesses “rele
vant information” that we are “likely to consider.” Ante, at
14, 16. Nonparties often do, but that is not a “compelling
interest” justifying intervention. I have little doubt that
Philadelphia possessed pertinent information in New
Jersey v. New York, but we did not permit Philadelphia to
intervene on that ground. Parties to litigation have ready
means of access to relevant information held by nonpar
ties, and those nonparties can certainly furnish such
information on their own if they consider it in their best
interests (through, for example, participation as amici
curiae).
   The majority also states that Duke Energy has compel
ling interests in its hydroelectric operations along the
river, and in “the amount of water that Duke Energy
needs to sustain its operations and provide electricity to
the region.” Ante, at 15. These are simply interests in a
particular use of water or its flow. Even if Duke Energy
uses water for particularly important purposes, its inter
ests are no different in kind from the interests of any other
entity that relies on water for its commercial operations.
   Finally, the majority asserts that Duke Energy “has a
unique and compelling interest in protecting the terms of
its existing [Federal Energy Regulatory Commission
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                   Opinion of ROBERTS, C. J.

(FERC)] license and the [Comprehensive Licensing Agree
ment (CRA)] that forms the basis of Duke Energy’s pend
ing renewal application.” Ibid. And the majority contends
that neither State represents these interests because
“[n]either State has signed the CRA or expressed an inten
tion to defend its terms,” and because North Carolina has
even expressed its intent to challenge the terms of the
CRA in this action. Ante, at 16.
   Again, all this amounts to is an articulation of the rea
son Duke Energy asserts a particular interest in the wa
ters of the Catawba. Other citizens of North Carolina
doubtless have reasons of their own, ones they find as
important as Duke Energy believes its to be. Weighing
those interests is an “intramural” matter for the State.
New Jersey v. New York, supra, at 373. In addition, the
Federal Government is doubtless familiar with the pend
ing FERC proceedings, and it sees no corresponding need
for us to grant Duke Energy’s motion to intervene. See
Brief for United States as Amicus Curiae 20, n. 3.
   As for CRWSP, the Special Master concluded that it
should be allowed to intervene, but only because its posi
tion was “similar analytically to Charlotte’s.” First In
terim Report of Special Master, O. T. 2008, No. 138, Orig.,
p. 25. The Court rejects Charlotte’s motion, but nonethe
less allows CRWSP to intervene on a ground not relied
upon by the Special Master. According to the majority,
CRWSP should be allowed to intervene because, as a
bistate entity, its full range of interests cannot be repre
sented entirely by either North or South Carolina. See
ante, at 11–14.
   CRWSP’s motion arguably presents a different case
from that of Duke Energy, one not definitively resolved by
this Court in New Jersey v. New York. At the end of the
day, however, I agree with the Special Master’s premise—
CRWSP’s position is really no different from Charlotte’s. I
disagree with her conclusion, of course, because I agree
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                    Opinion of ROBERTS, C. J.

with the Court that Charlotte should not be allowed to
intervene.
   A bistate entity cannot be allowed to intervene merely
because it embodies an “intermingling of state interests.”
Ante, at 13, n. 6. The same would be true of any bistate
entity, or indeed any corporation or individual conducting
business in both States. An exception for such cases
would certainly swallow the New Jersey v. New York rule.
Entities with interests in both States must seek to vindi
cate those interests within each State. Bistate entities are
not States entitled to invoke our original jurisdiction, and
should not be effectively accorded an automatic right to
intervene as parties in cases within that jurisdiction.
   With respect to both Duke Energy and CRWSP, the
majority further relies on its conclusion that the States
will not “properly represent” the interests of those entities.
Ante, at 13; see ante, at 16. If by that the Court means
that the States may adopt positions adverse to Duke
Energy and CRWSP, that surely cannot be enough. The
guiding principle articulated in New Jersey v. New York is
“that the state, when a party to a suit involving a matter
of sovereign interest, ‘must be deemed to represent all its
citizens,’ ” and may not be “judicially impeached on mat
ters of policy by its own subjects.” 345 U. S., at 372–373
(quoting Kentucky v. Indiana, 281 U. S., at 173–174). This
case involves a “matter of sovereign interest”—the equita
ble apportionment of water—and the States therefore
“properly represen[t]” the shared interests in water of “all”
their citizens, including Duke Energy and CRWSP. 345
U. S., at 372–373. An interest is “not properly repre
sented” by a State, id., at 373, when it is not a sovereign
interest but instead a parochial one, such as the interests
held to justify intervention in the cases on which the
majority relies. See supra, at 7–8.
   The majority also pays little heed to the practical con
straints on this Court’s original jurisdiction. It is hard to
12         SOUTH CAROLINA v. NORTH CAROLINA

                   Opinion of ROBERTS, C. J.

see how the arguments the Court accepts today could not
also be pressed by countless other water users in either
North or South Carolina. Under the Court’s analysis, I
see “no practical limitation on the number of citizens, as
such, who would be entitled to be made parties.” New
Jersey v. New York, supra, at 373. To the extent interven
tion is allowed for some private entities with interests in
the water, others who also have an interest will feel com
pelled to intervene as well—and we will be hard put to
refuse them. See Utah v. United States, 394 U. S., at 95–
96 (denying intervention to a corporation that sought to
quiet its title to land because, “[i]f [it were] admitted,
fairness would require the admission of any of the other
120 private landowners who wish to quiet their title . . . ,
greatly increasing the complexity of this litigation”). An
equitable apportionment action will take on the character
istics of an interpleader case, with all those asserting
interests in the limited supply of water jostling for their
share like animals at a water hole. And we will find our
selves in a “quandary whereby we must opt either to pick
and choose arbitrarily among similarly situated litigants
or to devote truly enormous portions of our energies to
[original] matters.” Ohio v. Wyandotte Chemicals Corp.,
401 U. S., at 504.
   Allowing nonsovereign entities to intervene as parties
will inevitably prolong the resolution of this and other
equitable apportionment actions, which already take
considerable time. Intervenors do not come alone—they
bring along more issues to decide, more discovery re
quests, more exceptions to the recommendations of the
Special Master. In particular, intervention makes settling
a case more difficult, as a private intervenor has the right
to object to a settlement agreement between the States, if
not the power to block a settlement altogether. Cf. Fire
fighters v. Cleveland, 478 U. S. 501, 529 (1986).
   And all this for what? The Special Master, and through
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                        Opinion of ROBERTS, C. J.

her the Court, can have the benefit of the views of those
seeking to intervene by according them the status of amici
curiae. “Where he presents no new questions, a third
party can contribute usually most effectively and always
most expeditiously by a brief amicus curiae and not by
intervention.” Bush v. Viterna, 740 F. 2d 350, 359 (CA5
1984) (per curiam) (internal quotation marks omitted).
Courts often treat amicus participation as an alternative
to intervention. See 7C C. Wright, A. Miller, & M. Kane,
Federal Practice and Procedure §1913, p. 495, and n. 26
(2007) (citing examples). And this Court often denies
motions to intervene while granting leave to participate as
an amicus in original actions generally, see, e.g., Kentucky
v. Indiana, 445 U. S. 941 (1980); United States v. Califor
nia, 377 U. S. 926 (1964); cf. New Hampshire v. Maine,
426 U. S. 363, 365, n. 2 (1976), and in equitable appor
tionment actions specifically, see, e.g., Arizona v. Califor
nia, 530 U. S. 392, 419, n. 6 (2000); Nebraska v. Wyoming,
507 U. S. 584, 589–590 (1993).
   Nebraska v. Wyoming is particularly instructive on this
point. The Court there adopted the recommendation of
the Special Master to deny intervention to certain entities.
See id., at 589–590; Second Interim Report of Special
Master, O. T. 1991, No. 108, Orig., pp. 108–109. The
interests of those entities in the water dispute were quite
similar to the interests of the entities seeking to intervene
here: One operated a powerplant and a reservoir on the
Laramie River, and another was a power district seeking
to protect its FERC license. See First Interim Report of
Special Master, O. T. 1988, No. 108, Orig., pp. 11–14, 9a.
While it adopted the Special 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 major
——————
 2 No   party filed exceptions to the Special Master’s recommendation to
14           SOUTH CAROLINA v. NORTH CAROLINA

                       Opinion of ROBERTS, C. J.

ity 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
respect to particular uses asserted by private entities.
Allowing intervention by such entities would vastly com
plicate and delay already complicated and lengthy actions.
And the benefits private entities might bring can be read
ily secured, as has typically been done, by their participa
tion 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 under
stand 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.




——————
deny intervention in Nebraska v. Wyoming. The Special Master later
allowed one of the entities, Basin Electric Power Cooperative, to inter
vene 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.
