One of the four “potential limiting principles” the Court offered for its Second Amendment analysis, is that Section 922(g)(4)—which permanently bars those previously involuntarily committed to a mental institution from possessing firearms—“punishes potentially non-volitional conduct.” The Court described the prohibition as “target[ing] the non-volitional act of being committed,” and pointed out that “[t]he underlying behavior that prompted the commitment may also be non-volitional.” The Court appeared to be suggesting that, by barring the previously committed from possessing guns, Section 922(g)(4) “made a criminal offense of mental illness.” See p.43 n.38 (quoting Robinsonv. California, 370 U.S. 660, 666 (1962) (striking down a state law criminalizing simply “be[ing] addicted to . . . narcotics”)).
Although the Court appeared to view Section 922(g)(4) as punishing mental illness, it did recognize that the “compelling interests” served by Section 922(g)(4) are the prevention of crime and suicide, see p.27-28, (as opposed to punishment). It would seem then that strict scrutiny’s narrow-tailoring analysis could be satisfied by demonstrating that the regulated class reasonably captures those who are a danger to themselves or others, even if the danger is not volitional on the part of class members. It does not seem likely that the Court would strike down a law banning gun possession by the involuntarily dangerous.
Given the Court’s description of the volitional/non-volitional distinction as a “limiting principle,” perhaps its rationale was that volitional conduct acts as a sort of Second Amendment waiver. In other words, when a class is defined by some volitional conduct, its firearm possession may be constitutionally restricted even if evidence of the class’s danger is not quite strong enough to satisfy strict scrutiny, because the members can choose whether or not to engage in the conduct. If so, it will be interesting to see how that principle would be applied in a situation where the volitional conduct in question is legal—a possibility that must have been contemplated by the Court, which listed the distinction between law-abiding and non-law-abiding individuals as a separate limiting principle.