The Supreme Court has granted cert in U.S. v. Hemani, which concerns the constitutionality of 18 U.S.C. § 922(g)(3), which forbids a person from possessing a firearm in or affecting commerce if he "is an unlawful user of … any controlled substance." The United States just filed its opening brief, stating: "At issue here is Section 922(g)(3)'s disarmament of a defined class of people—habitual users of controlled substances, i.e., those who regularly and unlawfully use drugs that are subject to the Controlled Substances Act, 21 U.S.C. 801 et seq. That restriction is temporary and limited: a person regains his ability to possess arms as soon as he stops habitually using drugs."
The ban applies only to someone who "is an unlawful user of or addicted to" a controlled substance, and the U.S. brief states:
courts of appeals have uniformly determined that a person is a "user" of a controlled substance within the meaning of Section 922(g)(3) only if he engages in the habitual or regular use of a controlled substance. That interpretation reflects the ordinary meaning of Section 922(g)(3)'s text. In this context, the verb "use" means "to take or consume (an alcoholic drink, a narcotic drug) regularly or habitually."