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Page Number: 23.0

18 

DEPARTMENT OF HOMELAND SECURITY v. 
REGENTS OF UNIV. OF CAL. 
Opinion of the Court 

Respondents maintain that this explanation is deficient 
for three reasons.  Their first and second arguments work
in tandem, claiming that the Duke Memorandum does not 
adequately explain the conclusion that DACA is unlawful, 
and  that  this  conclusion  is,  in  any  event,  wrong.    While 
those arguments carried the day in the lower courts, in our 
view they overlook an important constraint on Acting Sec-
retary Duke’s decisionmaking authority—she was bound by
the Attorney General’s legal determination. 

The same statutory provision that establishes the Secre-
tary of Homeland Security’s authority to administer and en-
force  immigration  laws  limits  that  authority,  specifying
that, with respect to “all questions of law,” the determina-
tions  of  the  Attorney  General  “shall  be  controlling.”  8 
U. S. C.  §1103(a)(1).    Respondents  are  aware  of  this  con-
straint.  Indeed they emphasized the point in the reviewa-
bility  sections  of  their  briefs.  But  in  their  merits  argu-
ments,  respondents  never  addressed  whether  or  how  this
unique statutory provision might affect our review.  They
did not discuss whether Duke was required to explain a le-
gal conclusion that was not hers to make.  Nor did they dis-
cuss  whether  the  current  suits  challenging  Duke’s  rescis-
sion decision, which everyone agrees was within her legal
authority under the INA, are proper vehicles for attacking
the Attorney General’s legal conclusion. 

Because of these gaps in respondents’ briefing, we do not
evaluate  the  claims  challenging  the  explanation  and  cor-
rectness of the illegality conclusion.  Instead we focus our 
attention on respondents’ third argument—that Acting Sec-
retary  Duke  “failed  to  consider  . . .  important  aspect[s]  of
the  problem”  before  her.  Motor  Vehicle  Mfrs.  Assn.  of 
United States, Inc. v. State Farm Mut. Automobile Ins. Co., 
463 U. S. 29, 43 (1983). 

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carried any independent weight.