Document ID: ./input/supremecourt_opinions/opinions/19pdf/18-587_5ifl.pdf
Page Number: 20.0

Cite as:  591 U. S. ____ (2020) 

15 

Opinion of the Court 

ensure that the rescission is not upheld on the basis of im-
permissible  “post  hoc  rationalization.”  Overton  Park,  401 
U. S., at 420.  But despite purporting to explain the Duke
Memorandum,  Secretary  Nielsen’s  reasoning  bears  little
relationship  to  that  of  her  predecessor.    Acting  Secretary
Duke rested the rescission on the conclusion that DACA is 
unlawful.  Period.  See App. to Pet. for Cert. 117a.  By con-
trast, Secretary Nielsen’s new memorandum offered three
“separate and independently sufficient reasons” for the re-
scission, id., at 122a, only the first of which is the conclusion
that DACA is illegal. 

Her second reason is that DACA is, at minimum, legally 
questionable and should be terminated to maintain public
confidence in the rule of law and avoid burdensome litiga-
tion.  No such justification can be found in the Duke Mem-
orandum.  Legal uncertainty is, of course, related to illegal-
ity.  But  the  two  justifications  are  meaningfully  distinct,
especially in this context.  While an agency might, for one 
reason or another, choose to do nothing in the face of uncer-
tainty,  illegality  presumably  requires  remedial  action  of 
some sort. 

The policy reasons that Secretary Nielsen cites as a third
basis for the rescission are also nowhere to be found in the 
Duke Memorandum.  That document makes no mention of 
a preference for legislative fixes, the superiority of case-by-
case decisionmaking, the importance of sending a message 
of  robust  enforcement,  or  any  other  policy  consideration. 
Nor are these points included in the legal analysis from the 
Fifth Circuit and the Attorney General.  They can be viewed
only  as  impermissible  post  hoc  rationalizations  and  thus 
are not properly before us.

The  Government,  echoed  by  JUSTICE  KAVANAUGH,  pro-
tests that requiring a new decision before considering Niel-
sen’s new justifications would be “an idle and useless for-
mality.”  NLRB v. Wyman-Gordon Co., 394 U. S. 759, 766,