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8 

ARIZONA v. NAVAJO NATION 

GORSUCH, J., dissenting 

the Colorado River, the Navajo Nation’s rights to use water 
from the Colorado River” have never been adjudicated.  Id., 
at 36.  The United States acknowledges that it holds certain 
water rights “in trust” for the Navajo.  See Tr. of Oral Arg. 
26,  40.  It  does  not  dispute  that  it  exercises  considerable 
control  over  the  disposition  of  water  from  the  Colorado
River.  And  it  concedes  that  the  Navajo’s  water  rights 
“may . . . include some portion of the mainstream of the Col-
orado.”  Id., at 33.  But instead of resolving what the Nav-
ajo’s  water  rights  might  be,  the  United  States  has  some-
times resisted efforts to answer that question. 

The  current  legal  regime  governing  the  Colorado  River
began  with  a  1922  interstate  compact  between  seven
States.  That  agreement  split  the  Colorado  into  two  ba-
sins—an  Upper  Basin  and  a  Lower  Basin.  See  Colorado 
River Compact, Art. II, Colo. Rev. Stat. §37–61–101 (2022). 
The  compact  answered  some  high-level  questions  about 
which States could lay claim to which sections of the river.
But  it  did  not  purport  to  “affec[t]  the  obligations  of  the 
United States of America to Indian [T]ribes.”  Id., Art. VII. 
In  that  way,  it  left  the  Navajo  with  no  insight  into  what
water they could claim as their own. 

Six years later, Congress entered the picture by passing
the Boulder Canyon Project Act, 45 Stat. 1057, codified at 
43 U. S. C. §§617–619b.  That Act had a profound impact on 
the Lower Basin.  It authorized the construction of the Hoo-
ver Dam and the creation of Lake Mead.  §617.  More than 
that, it gave the Secretary of the Interior substantial power
to divvy up the resulting impounded water.  Failing agree-
ment  among  the  States  in  the  region,  the  law  authorized 
the Secretary to enter into contracts for the delivery of wa-
ter  and  provided  that  “[n]o  person”  may  have  water  from 
the mainstream of the Colorado in the Lower Basin “except
by  contract.”    §617d;  see  also  Arizona  v.  California,  373 
U. S. 546, 565 (1963) (Arizona I ).  In adopting this law, Con-
gress hoped “to put an end to the long-standing dispute over