Document ID: ./input/supremecourt_opinions/opinions/22pdf/21-376_7l48.pdf
Page Number: 115.0

Cite as:  599 U. S. ____ (2023) 

33 

THOMAS, J., dissenting 

ers can operate only externally, in the context of lands un-
der  the  purview  of  another  sovereign  (like  Indian  tribal 
lands) or in the context of a government-to-government re-
lationship  (such  as  matters  of  diplomacy  or  peace).    See 
Curtiss-Wright, 299 U. S., at 315, 319.  But regulating child
custody proceedings of citizens within a State is the para-
digmatic  domestic  situation;  the  Federal  Government 
surely could not apply its foreign-affairs powers to the do-
mestic family-law or criminal matters of any other citizens
merely because they happened to have citizenship or ances-
tral connections with another nation.15  Apart from the sin-
gle  provision  that  allows  tribal  governments  jurisdiction
over proceedings for Indians on tribal lands, see §1911(a),
ICWA is completely untethered from any external aspect of 
our Nation that could somehow implicate these powers.

That should be the end of the analysis.  Again, as the ma-
jority notes, our Federal Government has only the powers 
that  the  Constitution  enumerates.  See  ante,  at  10–11; 
McCulloch, 4 Wheat., at 405.  Not one of those enumerated 
powers justifies ICWA.  Therefore, it has no basis whatso-
ever in our constitutional system. 

B 
Even taking our “plenary power” precedents as given (as 

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15 Indeed, ICWA stands in sharp contrast to statutes regarding inter-
national  adoptions,  in  accordance  with  the  Hague  Convention.    Those 
statutes generally regulate only adoptions by a foreign parent of a child 
residing  in  the  United  States,  or  vice  versa.    E.g.,  114  Stat.  825;  42 
U. S. C. §§14931, 14932.  In other words, there is a cross-border compo-
nent; the statutes do not regulate adoption proceedings merely because 
the child’s parents are, for example, dual Mexican-American citizens or 
dual Irish-American citizens.  For ICWA to be comparable to those stat-
utes,  it  could  regulate  only  the  adoption  of  children  who  reside  on  an
Indian reservation by parents who live within the sole jurisdiction of a
State, or vice versa.  While I take no position on whether such a more 
limited  law  would  be  constitutional,  that  stark  difference  only  under-
scores ICWA’s lack of any external focus.