Document ID: ./input/supremecourt_opinions/opinions/22pdf/22-58_i425.pdf
Page Number: 47

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

5 

ALITO, J., dissenting 

discretion when it comes to the arrest and release of crimi-
nal aliens.”  Nielsen v. Preap, 586 U. S. ___, ___ (2019) (slip 
op., at 15) (emphasis in original).

Two  such  limits  are  important  here.    First,  8  U. S. C. 
§1226(c) directs the Government to “take into custody any 
alien” inadmissible or deportable on certain criminal or ter-
rorist  grounds  “when  the  alien  is  released”  from  criminal 
custody,  including  when  such  an alien is  released  on  “pa-
role,  supervised  release,  or  probation.”    Second,  §1231(a) 
Section 
imposes  a  categorical  detention  mandate. 
1231(a)(2) provides that the Government “shall detain [an]
alien” “[d]uring the removal period,” which often begins ei-
ther when  an “order of removal becomes administratively 
final” or when an “alien is released from detention or con-
finement”  not  arising 
immigration  process,
§1231(a)(1)(B).  This requirement is reinforced by the direc-
tion that “[u]nder no circumstance during the removal pe-
riod  shall  the  [Government]  release  an  alien”  found  inad-
missible  or  deportable  under  almost  any  of  the  grounds
relevant under §1226(c).  §1231(a)(2).  And §1231(a)(1)(A)
commands  that  the  Government  “shall  remove  the  alien” 
within the removal period. 

from 

All of our recent decisions interpreting these provisions
confirm that, for covered aliens, shall means shall; it does 
not mean “may.”  See Johnson v. Guzman Chavez, 594 U. S. 
___, ___–___, and n. 2 (2021) (slip op., at 2–3, and n. 2); Niel-
sen, 586 U. S., at ___–___ (slip op., at 16–17).  Until quite
recently, that was the Government’s understanding as well.
See Biden v. Texas, 597 U. S. ___, ___–___ (2022) (slip op., 
at 8–9) (ALITO, J., dissenting).

Actions taken by Congress when IIRIRA was enacted un-
derscore this conclusion.  Because the provisions described
above left the Executive with no discretion to refrain from 
arresting  and  detaining  covered  aliens,  even  during  the
time immediately after IIRIRA’s enactment when the Exec-
utive  was  still  “expand[ing]  its  capacities”  to  enforce  the