Do we have to wait for legislators to ban bump stocks?
<p>Do legislators actually have to take the step of banning bump stocks, or could the ATF (or other government agency) unilaterally state that the addition of one to a weapon means that it now has all of the attributes of a <em>Machine Gun</em> as defined in the <a href="https://archive.org/stream/NationalFirearmsActOf1934/National_Firearms_Act_of_1934_djvu.txt" rel="nofollow noreferrer">National Firearms Act of 1934</a>?</p>

<blockquote>
  <p>"Machine gun." (b) The term "machine gun " means any weapon which shoots, 
  or is designed to shoot, automatically or semiautomatically, more 
  than one shot, without manual reloading, by a single function of 
  the trigger.</p>
</blockquote>

<p>My intuition is that if the answer is "yes," then owners of bump stocks could still own them without breaking the law, they just won't ever be able to apply that accessory to their weapons without running afoul of the National Firearms Act and risking a $2,000 fine and 5 years in jail. Is this understanding of how the law works correct?</p>

<p>Under current <a href="https://www.gpo.gov/fdsys/pkg/FR-2017-12-26/pdf/2017-27898.pdf" rel="nofollow noreferrer">federal law</a>, we would have to wait for some legislative body to change the law. If ATF changes the federal regulations, they might be classed as <a href="https://www.law.cornell.edu/uscode/text/26/5845" rel="nofollow noreferrer">"machine guns"</a> (under the "frame designed for converting" clause), which are banned. As the above Docket No. 2017R–22 (from December 26, 2017) says, DoJ expects to plan to discuss changing the rules. They might then be outlawed by executive action (though a court test could be necessary, since executive wish is not the final word on interpreting statutes). </p>

<p>The relevant part of the definition of machine gun, which could apply to bump stocks, is:</p>

<blockquote>
  <p>The term shall also include <em>the frame or receiver</em> of any such weapon,
  any part designed and intended solely and exclusively, or combination
  of parts designed and intended, <em>for use in converting a weapon into a
  machinegun</em>, and any combination of parts from which a machinegun can
  be assembled if such parts are in the possession or under the control
  of a person.</p>
</blockquote>

<p>But "such" weapon is one that</p>

<blockquote>
  <p>shoots, is designed to shoot, or can be readily restored to shoot,
  automatically more than one shot, without manual reloading, by a
  <em>single function of the trigger</em></p>
</blockquote>

<p>The definition does not say anything about a single finger action, so there is a reasonable probability that including bump stocks within the scope of existing legislation would be held to exceed congressional authority.</p>

united-states criminal-law firearms