Document ID: ./input/supremecourt_opinions/opinions/19pdf/18-9526_9okb.pdf
Page Number: 23.0

20 

MCGIRT v. OKLAHOMA 

Opinion of the Court 

compelling” form of evidence.  Id., at 356.  Both cases em-
phasized that what value such evidence has can only be in-
terpretative—evidence  that,  at  best,  might  be  used  to  the 
extent it sheds light on what the terms found in a statute 
meant at the time of the law’s adoption, not as an alterna-
tive means of proving disestablishment or diminishment. 

To avoid further confusion, we restate the point.  There 
is no need to consult extratextual sources when the mean-
ing  of  a  statute’s  terms  is  clear.    Nor  may  extratextual 
sources overcome those terms.  The only role such materials
can properly play is to help “clear up . . . not create” ambi-
guity about a statute’s original meaning.  Milner v. Depart-
ment of Navy, 562 U. S. 562, 574 (2011).  And, as we have 
said time and again, once a reservation is established, it re-
tains that status “until Congress explicitly indicates other-
wise.”  Solem, 465 U. S., at 470 (citing Celestine, 215 U. S., 
at 285); see also Yankton Sioux, 522 U. S., at 343 (“[O]nly 
Congress can alter the terms of an Indian treaty by dimin-
ishing a reservation, and its intent to do so must be clear
and plain”) (citation and internal quotation marks omitted). 
The dissent charges that we have failed to take account 
of the “compelling reasons” for considering extratextual ev-
idence as a matter of course.  Post, at 11–12.  But Oklahoma 
and the dissent have cited no case in which this Court has 
found a reservation disestablished without first concluding
that a statute required that result.  Perhaps they wish this 
case  to  be  the  first.    To  follow  Oklahoma  and  the  dissent 
down  that  path,  though,  would  only  serve  to allow  States 
and courts to finish work Congress has left undone, usurp 

—————— 
dence in our diminishment analysis, for ‘[e]very surplus land Act neces-
sarily resulted in a surge of non-Indian settlement and degraded the “In-
dian character” of the reservation, yet we have repeatedly stated that not 
every  surplus  land  Act  diminished  the  affected  reservation.’  Yankton 
Sioux, 522 U. S., at 356. . . .  Evidence of the subsequent treatment of the 
disputed land by Government officials likewise has ‘limited interpretive 
value.’ Id., at 355.”  577 U. S., at ___ (slip op., at 11).