Document ID: ./input/supremecourt_opinions/opinions/23pdf/22-976_e29g.pdf
Page Number: 17

Cite as:  602 U. S. ____ (2024) 

13 

Opinion of the Court 

(opinion  of 

  See  post,  at  7–9 

similar  reasoning. 
SOTOMAYOR, J.). 
  This argument rests on the mistaken premise that there 
is a difference between a shooter flexing his finger to pull 
the  trigger  and  a  shooter  pushing  the  firearm  forward  to 
bump  the  trigger  against  his  stationary  finger.    ATF  and 
the  dissent  seek  to  call  the  shooter’s  initial  trigger  pull  a 
“function  of  the  trigger”  while  ignoring  the  subsequent 
“bumps”  of  the  shooter’s  finger  against  the  trigger  before 
every additional shot.  But, §5845(b) does not define a ma-
chinegun based on what type of human input engages the 
trigger—whether it be a pull, bump, or something else.  Nor 
does it define a machinegun based on whether the shooter 
has assistance engaging the trigger.  The statutory defini-
tion instead hinges on how many shots discharge when the 
shooter engages the trigger.  And, as we have explained, a 
semiautomatic  rifle  will  fire  only  one  shot  each  time  the 
shooter  engages  the  trigger—with  or  without  a  bump 
stock.6  Supra, at 7–12. 
  In any event, ATF’s argument cannot succeed on its own 
terms.    The  final  Rule  defines  “function  of  the  trigger”  to 
include not only “a single pull of the trigger” but also any 
“analogous  motions.”    83  Fed.  Reg.  66553.    ATF  concedes 
that  one such  analogous  motion that  qualifies  as  a  single 
function of the trigger is “sliding the rifle forward” to bump 
the  trigger.    Brief  for  Petitioners  22.    But,  if  that  is  true, 
then every bump is a separate “function of the trigger,” and 
semiautomatic rifles equipped with bump stocks are there-
fore not machineguns.  ATF resists the natural implication 

—————— 

6

 The dissent says that we “resis[t]” the “ordinary understanding of the 
term ‘function of the trigger’ with two technical arguments.”  Post, at 10.  
But, the arguments it refers to explain why, even assuming a semiauto-
matic rifle equipped with a bump stock could fire more than one shot by 
a single function of the trigger, it could not do so “automatically.”  See 
infra, at 14–17.  Those arguments have nothing to do with our explana-
tion of what a “single function of the trigger” means.  Ibid.