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

§701(a)(1),  or  that  the  “agency  action  is  committed  to
agency discretion by law,” §701(a)(2).  The latter exception
is at issue here. 

To “honor the presumption of review, we have read the
exception in §701(a)(2) quite narrowly,”  Weyerhaeuser  Co. 
v. United States Fish and Wildlife Serv., 586 U. S. ___, ___ 
(2018) (slip op., at 12), confining it to those rare “adminis-
trative  decision[s]  traditionally  left  to  agency  discretion,” 
Lincoln v. Vigil, 508 U. S. 182, 191 (1993).  This limited cat-
egory of unreviewable actions includes an agency’s decision 
not  to  institute  enforcement  proceedings,  Heckler  v. 
Chaney, 470 U. S. 821, 831–832 (1985), and it is on that ex-
ception that the Government primarily relies.

In  Chaney,  several  death-row  inmates  petitioned  the 
Food and Drug Administration (FDA) to take enforcement
action  against  two  States  to  prevent  their  use  of  certain
drugs for lethal injection.  The Court held that the FDA’s 
denial of that petition was presumptively unreviewable in 
light  of  the  well-established  “tradition”  that  “an  agency’s
decision not to prosecute or enforce” is “generally commit-
ted  to  an  agency’s  absolute  discretion.”    Id.,  at  831.  We 
identified a constellation of reasons that underpin this tra-
dition.  To start, a non-enforcement decision “often involves 
a  complicated  balancing  of  a  number  of  factors  which 
are  peculiarly  within  [the  agency’s]  expertise,”  such  as 
“whether the particular enforcement action requested best 
fits the agency’s overall policies.”  Ibid.  The decision also 
mirrors, “to some extent,” a prosecutor’s decision not to in-
dict, which has “long been regarded as the special province
of the Executive Branch.”  Id., at 832.  And, as a practical 
matter, “when an agency refuses to act” there is no action 
to “provide[ ] a focus for judicial review.”  Ibid. 

The Government contends that a general non-enforcement
policy  is  equivalent  to  the  individual  non-enforcement 
decision at issue in Chaney.  In each case, the Government 
argues, the agency must balance factors peculiarly within