(Slip Opinion) OCTOBER TERM, 2017 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 

TEXAS v. NEW MEXICO ET AL. 

ON EXCEPTIONS TO REPORT OF SPECIAL MASTER 

No. 141, Orig. Argued January 8, 2018—Decided March 5, 2018 

To resolve their disputes over water rights in the Rio Grande, Colorado, 

New Mexico, and Texas, with Congress’s approval, signed the Rio

Grande Compact. The Compact requires Colorado to deliver a specified amount of water annually to New Mexico at the state line and 

directs New Mexico to deliver a specified amount of water to the Elephant Butte Reservoir. The Reservoir was completed in 1916 as part 

of the Federal Government’s Rio Grande Project and plays a central

role in fulfilling the United States’s obligations to supply water under 

a 1906 treaty with Mexico as well as under several agreements with

downstream water districts in New Mexico and Texas (Downstream 

Contracts). 

 Texas brought this original action complaining that New Mexico 

has violated the Compact by allowing downstream New Mexico users 

to siphon off water below the Reservoir in ways not anticipated in the

Downstream Contracts. The United States intervened and filed a 

complaint with parallel allegations. The Special Master filed a report

recommending that the United States’s complaint be dismissed in

part because the Compact does not confer on the United States the

power to enforce its terms. This Court agreed to hear two exceptions 

to the report concerning the scope of the claims the United States can 

assert here: The United States says it may pursue claims for Compact violations; Colorado says the United States should be permitted

to pursue claims only to the extent they arise under the 1906 treaty

with Mexico. 

Held: The United States may pursue the Compact claims it has pleaded 

in this original action. This Court, using its unique authority to mold 

original actions, see Kansas v. Nebraska, 574 U. S. ___, ___, has 

sometimes permitted the federal government to participate in compact suits to defend “distinctively federal interests” that a normal lit-
 

 

2 TEXAS v. NEW MEXICO 

Syllabus 

igant might not be permitted to pursue in traditional litigation, Maryland v. Louisiana, 451 U. S. 725, 745, n. 21. While this permission

should not be confused with license, several considerations taken collectively lead to the conclusion that the United States may pursue 

the particular claims it has pleaded in this case. First, the Compact

is inextricably intertwined with the Rio Grande Project and the 

Downstream Contracts. Second, New Mexico has conceded in pleadings and at oral argument that the United States plays an integral 

role in the Compact’s operation. Third, a breach of the Compact

could jeopardize the federal government’s ability to satisfy its treaty

obligations to Mexico. Fourth, the United States has asserted its 

Compact claims in an existing action brought by Texas, seeking substantially the same relief and without that State’s objection. This 

case does not present the question whether the United States could

initiate litigation to force a State to perform its obligations under the

Compact or expand the scope of an existing controversy between

States. Pp. 4–7. 

United States’s exception sustained; all other exceptions overruled; and 

case remanded. 

GORSUCH, J., delivered the opinion for a unanimous Court. 
 

 

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Cite as: 583 U. S. ____ (2018) 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, Washington, 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. 141, Orig. 

STATE OF TEXAS, PLAINTIFF v. STATE OF
 

NEW MEXICO AND STATE OF COLORADO 

ON EXCEPTIONS TO REPORT OF SPECIAL MASTER 

[March 5, 2018]

 JUSTICE GORSUCH delivered the opinion of the Court. 

Will Rogers reportedly called the Rio Grande “the only 

river I ever saw that needed irrigation.” In its long journey from the Colorado Rockies to the Gulf of Mexico, many 

and sometimes competing demands are made on the river’s resources. In an effort to reconcile some of those 

demands, Colorado, New Mexico, and Texas, acting with

the federal government’s assent, signed the Rio Grande

Compact in the 1930s. In today’s lawsuit, Texas claims

that New Mexico has defied the Compact. But at this 

stage in the proceedings we face only a preliminary and

narrow question: May the United States, as an intervenor,

assert essentially the same claims Texas already has? We 

believe it may. 

Like its namesake, the Rio Grande Compact took a long

and circuitous route to ratification. Its roots trace perhaps

to the 1890s, when Mexico complained to the United 

States that increasing demands on the river upstream left 

little for those below the border. The federal government

responded by proposing, among other things, to build a 

reservoir and guarantee Mexico a regular and regulated

release of water. Eventually, the government identified a 
 

 

 

2 TEXAS v. NEW MEXICO 

Opinion of the Court 

potential dam site near Elephant Butte, New Mexico,

about 105 miles north of the Texas state line. The government presented this suggestion to representatives of 

Mexico and the affected States in a 1904 “‘Irrigation Congress,’” where it was “‘heartily endorse[d] and approve[d].’” Official Proceedings of the Twelfth National 

Irrigation Congress 107 (G. Mitchell ed. 1905). So, in 

1906, the United States agreed by treaty to deliver 60,000

acre-feet of water annually to Mexico upon completion of 

the new reservoir. Convention Between the United States 

and Mexico Providing for the Equitable Distribution of the

Waters of the Rio Grande for Irrigation Purposes, 34 Stat.

2953. After obtaining the necessary water rights, the 

United States began construction of the dam in 1910 and 

completed it in 1916 as part of a broader infrastructure 

development known as the Rio Grande Project. 

But that still left the problem of resolving similar disputes among the various States. After a number of interim 

agreements and impasses, the affected parties eventually (and nearly simultaneously) negotiated several 

agreements. And here again the Rio Grande Project and 

its Elephant Butte Reservoir played a central role. In the 

first set of agreements, the federal government promised

to supply water from the Reservoir to downstream water

districts with 155,000 irrigable acres in New Mexico and 

Texas. In turn, the water districts agreed to pay charges

in proportion to the percentage of the total acres lying in

each State—roughly 57% for New Mexico and 43% for 

Texas. We will call those agreements the “Downstream 

Contracts.” Additionally, Colorado, New Mexico, and

Texas concluded the Rio Grande Compact, which Congress

approved in 1939. Act of May 31, 1939, 53 Stat. 785. In 

the Compact, the parties indicated that nothing in their 

agreement should be “construed as affecting” the federal 

government’s treaty duties to deliver promised water to 

Mexico, but only as resolving disputes among themselves. 
Cite as: 583 U. S. ____ (2018) 3 

Opinion of the Court 

Id., at 792. Toward that end, the Compact required Colorado to deliver a specified amount of water annually to

New Mexico at the state line. Id., at 787–788. But then, 

instead of similarly requiring New Mexico to deliver a

specified amount of water annually to the Texas state line, 

the Compact directed New Mexico to deliver water to the 

Reservoir. Id., at 788.* In isolation, this might have

seemed a curious choice, for a promise to deliver water to a 

reservoir more than 100 miles inside New Mexico would 

seemingly secure nothing for Texas. But the choice made 

all the sense in the world in light of the simultaneously 

negotiated Downstream Contracts that promised Texas 

water districts a certain amount of water every year from

the Reservoir’s resources. 

Fast forward to this dispute. Texas filed an original

action before this Court complaining that New Mexico has

violated the Compact. According to Texas, New Mexico is

effectively breaching its Compact duty to deliver water to

the Reservoir by allowing downstream New Mexico users

to siphon off water below the Reservoir in ways the Downstream Contracts do not anticipate. After we permitted

the United States to intervene, it also filed a complaint 

with allegations that parallel Texas’s. In response to

these complaints, New Mexico filed a motion to dismiss. A 

Special Master we appointed to consider the case received

briefing, heard argument, and eventually issued an interim report recommending that we deny New Mexico’s 

motion to dismiss Texas’s complaint. We accepted that 

recommendation. At the same time, the Master recom-

—————— 

*To be precise, the Compact originally required New Mexico to deliver

water to a measuring station at San Marcial, New Mexico, upstream

of the Elephant Butte Reservoir. 53 Stat. 788. But the Compact also

established something called the Rio Grande Compact Commission and 

gave it the power to administer the Compact in various ways. Id., at 

791. In 1948, that Commission relocated the spot for measuring the 

delivery obligation from the measuring station to the Reservoir itself. 
 

4 TEXAS v. NEW MEXICO 

Opinion of the Court 

mended that we dismiss in part the complaint filed by the

United States. The Master reasoned, in pertinent part, 

that the Compact does not confer on the United States the 

power to enforce its terms. In response to the Master’s 

report, the parties filed a number of exceptions. We 

agreed to hear two of these exceptions—one by the United 

States and one by Colorado—concerning the scope of the 

claims the United States can assert in this original action. 

The United States says it may pursue claims for violations 

of the Compact itself; Colorado says the United States

should be permitted to pursue claims only to the extent 

they arise under the 1906 treaty with Mexico. 

Our analysis begins with the Constitution. Its Compact

Clause provides that “[n]o State shall, without the Consent of Congress, . . . enter into any Agreement or Compact with another State.” Art. I, §10, cl. 3. Congress’s

approval serves to “prevent any compact or agreement 

between any two States, which might affect injuriously the 

interests of the others.” Florida v. Georgia, 17 How. 478, 

494 (1855). It also ensures that the Legislature can “check 

any infringement of the rights of the national government.” 3 J. Story, Commentaries on the Constitution of 

the United States §1397, p. 272 (1833) (in subsequent

editions, §1403). So, for example, if a proposed interstate

agreement might lead to friction with a foreign country or 

injure the interests of another region of our own, Congress 

may withhold its approval. But once Congress gives its

consent, a compact between States—like any other federal 

statute—becomes the law of the land. Texas v. New Mexico, 

462 U. S. 554, 564 (1983).

Our role in compact cases differs from our role in ordinary litigation. The Constitution endows this Court with 

original jurisdiction over disputes between the States. See 

Art. III, §2. And this Court’s role in these cases is to serve 

“‘as a substitute for the diplomatic settlement of controversies between sovereigns and a possible resort to force.’” 
Cite as: 583 U. S. ____ (2018) 5 

Opinion of the Court 

Kansas v. Nebraska, 574 U. S. ___, ___ (2015) (slip op., at 

6) (quoting North Dakota v. Minnesota, 263 U. S. 365, 

372–373 (1923)). As a result, the Court may, “[i]n this 

singular sphere, . . . ‘regulate and mould the process it 

uses in such a manner as in its judgment will best promote the purposes of justice.’” 574 U. S., at ___–___ (slip 

op., at 6–7) (quoting Kentucky v. Dennison, 24 How. 66, 98 

(1861)).

Using that special authority, we have sometimes permitted the federal government to participate in compact

suits to defend “distinctively federal interests” that a

normal litigant might not be permitted to pursue in traditional litigation. Maryland v. Louisiana, 451 U. S. 725, 

745, n. 21 (1981). At the same time, our permission

should not be confused for license. Viewed from some 

sufficiently abstract level of generality, almost any compact between the States will touch on some concern of the 

national government—foreign affairs, interstate commerce, taxing and spending. No doubt that is the very

reason why the Constitution requires congressional ratification of state compacts. But just because Congress enjoys a special role in approving interstate agreements, it

does not necessarily follow that the United States has 

blanket authority to intervene in cases concerning the

construction of those agreements. 

Still, bearing in mind our unique authority to mold 

original actions, several considerations taken collectively 

persuade us that the United States may pursue the particular claims it has pleaded in this case: 

First, the Compact is inextricably intertwined with the

Rio Grande Project and the Downstream Contracts. The 

Compact indicates that its purpose is to “effec[t] an equitable apportionment” of “the waters of the Rio Grande” 

between the affected States. 53 Stat. 785. Yet it can 

achieve that purpose only because, by the time the Compact was executed and enacted, the United States had 
 

6 TEXAS v. NEW MEXICO 

Opinion of the Court 

negotiated and approved the Downstream Contracts, in 

which it assumed a legal responsibility to deliver a certain 

amount of water to Texas. In this way, the United States

might be said to serve, through the Downstream Contracts, as a sort of “‘agent’ of the Compact, charged with

assuring that the Compact’s equitable apportionment” to

Texas and part of New Mexico “is, in fact, made.” Texas’s 

Reply to Exceptions to the First Interim Report of the 

Special Master 40. Or by way of another rough analogy,

the Compact could be thought implicitly to incorporate the

Downstream Contracts by reference. Cf. 11 R. Lord, Williston on Contracts §30:26 (4th ed. 2017). However described, it is clear enough that the federal government has 

an interest in seeing that water is deposited in the Reservoir consistent with the Compact’s terms. That is what 

allows the United States to meet its duties under the 

Downstream Contracts, which are themselves essential to 

the fulfillment of the Compact’s expressly stated purpose. 

Second, New Mexico has conceded that the United 

States plays an integral role in the Compact’s operation. 

Early in these proceedings, it argued that the federal 

government was an indispensable party to this lawsuit 

because it is “responsible for . . . delivery of . . . water” as

required by the Downstream Contracts and anticipated by

the Compact. Brief in Opposition 33; ibid. (“[T]he entry of 

a Decree in accordance with Texas’ Prayer for Relief would 

necessarily affect the United States’ interests in the [Rio 

Grande] Project” contract). And at oral argument, New 

Mexico contended that the federal government is so integrally a part of the Compact’s operation that a State could 

sue the United States under the Compact for interfering 

with its operation. Tr. of Oral Arg. 59. 

Third, a breach of the Compact could jeopardize the

federal government’s ability to satisfy its treaty obligations. See Sanitary Dist. of Chicago v. United States, 266 

U. S. 405, 423–425 (1925) (recognizing the strong interests 
Cite as: 583 U. S. ____ (2018) 7 

Opinion of the Court 

of the United States in preventing interference with its

treaty obligations). Our treaty with Mexico requires the

federal government to deliver 60,000 acre-feet of water

annually from the Elephant Butte Reservoir. And to fill 

that Reservoir the Compact obliges New Mexico to deliver 

a specified amount of water to the facility. So a failure by

New Mexico to meet its Compact obligations could directly

impair the federal government’s ability to perform its 

obligations under the treaty. Now the Compact says

plainly that it may not be “construed as affecting the

obligations of the United States of America to Mexico” 

under existing treaties. 53 Stat. 792. But that means 

only that the Compact seeks to avoid impairing the federal 

government’s treaty obligations. Permitting the United 

States to proceed here will allow it to ensure that those

obligations are, in fact, honored. 

Fourth, the United States has asserted its Compact 

claims in an existing action brought by Texas, seeking

substantially the same relief and without that State’s 

objection. This case does not present the question whether

the United States could initiate litigation to force a State

to perform its obligations under the Compact or expand 

the scope of an existing controversy between States. 

Taken together, we are persuaded these factors favor

allowing the United States to pursue the Compact claims

it has pleaded in this original action. Nothing in our 

opinion should be taken to suggest whether a different 

result would obtain in the absence of any of the considerations we have outlined or in the presence of additional, 

countervailing considerations. The United States’s exception is sustained, all other exceptions are overruled, and

the case is remanded to the Special Master for further

proceedings consistent with this opinion. 

It is so ordered.