Document ID: ./input/supremecourt_opinions/opinions/22pdf/21-1484_aplc.pdf
Page Number: 1

(Slip Opinion) 

OCTOBER  TERM,  2022 

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 

ARIZONA ET AL. v. NAVAJO NATION ET AL. 

CERTIORARI TO THE UNITED STATES COURT OF APPEALS FOR 
THE NINTH CIRCUIT 

No. 21–1484.  Argued March 20, 2023—Decided June 22, 2023* 

An 1868 peace treaty between the United States and the Navajo Tribe 
established the Navajo Reservation that today spans some 17 million 
acres,  almost  entirely  in  the  Colorado  River  Basin  of  the  western 
United States.  The Federal Government’s reservation of land for an 
Indian tribe implicitly reserves the right to use needed water from var-
ious  sources—such  as  groundwater,  rivers,  streams,  lakes,  and 
springs—that  arise  on,  border,  cross,  underlie,  or  are  encompassed 
within the reservation.  See Winters v. United States, 207 U. S. 564, 
576–577.  While the Tribe has the right to use needed water from the 
reservation’s numerous water sources, the Navajos face the same wa-
ter scarcity problem that many in the western United States face.  In 
the Navajos’ view, the Federal Government’s efforts to assist the Nav-
ajos with their water needs did not fully satisfy the trust obligations of
the United States under the 1868 treaty.  The Navajos filed suit seek-
ing  to  compel  the  United  States  to  take  affirmative  steps  to  secure 
needed water for the Tribe—including by assessing the Tribe’s water 
needs, developing a plan to secure the needed water, and potentially
building pipelines, pumps, wells, or other water infrastructure.  The 
States of Arizona, Nevada, and Colorado intervened against the Tribe
to protect those States’ interests in water from the Colorado River.  The 
U. S. District Court for the District of Arizona dismissed the Navajo
Tribe’s complaint, but the Ninth Circuit reversed, holding in relevant 
part that the United States has a duty under the 1868 treaty to take
affirmative steps to secure water for the Navajos. 

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* Together with No. 22–51, Department of the Interior et al. v. Navajo 

Nation et al., also on certiorari to the same court.