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Page Number: 39

18 

ARIZONA v. NAVAJO NATION 

GORSUCH, J., dissenting 

promised large numbers of animals to the Tribe.  Art. XII, 
id., at 670.  Those guarantees take as a given that the Tribe
could access water sufficient to live, tend crops, and raise 
animals in perpetuity.

As we have seen, “the history of the treaty, the negotia-
tions, and the practical construction adopted by the parties” 
may also inform a treaty’s interpretation.  Choctaw Nation, 
318 U. S., at 432.  And here history is particularly telling.
Much  of  the  Navajo’s  plight  at  Bosque  Redondo  owed  to
both the lack of water and the poor quality of what water
did exist.  General Sherman appreciated this point and ex-
pressly raised the availability of water in his negotiations 
with the Tribe.  Treaty Record 5.  Doubtless, he did so be-
cause everyone had found the water at Bosque Redondo in-
sufficient and because the Navajo’s strong desire to return
home  rested  in  no  small  part  on  the  availability  of  water 
there.  Id., at 3, 8.  Because the Treaty of 1868 must be read
as the Navajo “themselves would have understood” it, Mille 
Lacs  Band,  526  U. S.,  at  196,  it  is  impossible  to  conclude
that water rights were not included.  Really, few points ap-
pear to have been more central to both parties’ dealings.

What water rights does the Treaty of 1868 secure to the
Tribe?  Remarkably, even today no one knows the answer. 
But at least we know the right question to ask:  How much 
is required to fulfill the purposes of the reservation that the
Treaty of 1868 established?  See Nevada v. United States, 
463 U. S. 110, 116, n. 1 (1983) (citing cases).  We know, too, 
that a Tribe’s Winters rights are not necessarily limited to
the water sources found within the corners of their reserva-
tion.  Winters itself involved a challenge to the misappropri-
ation  of  water  by  upstream  landowners  from  a  river  that
ran along the border of tribal lands.  207 U. S., at 576.  And 
here the Navajo’s Reservation likewise stands adjacent to a
long stretch of the Colorado River flowing through both its 
Upper and Lower Basins.  App. 91.  Finally, we know that