The Ninth Circuit stated in Castillo-Rivera that a conviction under Penal Code 12021(a) may not constitute an aggravated felony because it covers those addicted to the use of any narcotic drug[,] 244 F.3d at 1022-23 (emphasis added). Both Penal Code 12021(a)(1) and 18 U.S.C. 922(g) make it a crime for persons addicted to certain substances to possess a firearm, but the California prohibition is broader than the federal statute in two regards.

Penal Code 12021(a)(1) prohibits [a]ny person . . . who is addicted to the use of narcotic drugs from possessing a firearm, while 18 U.S.C. 922(g)(3) proscribes the possession of a firearm by any person . . . who is an unlawful user of or addicted to any controlled substance (as defined in section 102 of the Controlled Substances Act [CSA] (21 U.S.C. 802)). The California statute is broader with regard to both the substances it regulates and the consumers it prohibits from possessing a firearm.

Under California law, [w]henever reference is made to the term narcotics in any provision of law outside [the Uniform Controlled Substances Act], unless otherwise expressly provided, it shall be construed to mean controlled substances classified in Schedules I and II of the Uniform Controlled Substances Act. Health & Safety Code 11032 (West 2007). The Ninth Circuit has note[d] that California law regulates the possession and sale of numerous substances that are not similarly regulated by the federal CSA. Ruiz-Vidal v. Gonzales, 473 F.3d 1072, 1078, 1078 n.6 (9th Cir. 2007); People v. Boultinghouse, 134 Cal.App.4th 619, 622 (2005) (California Schedule I regulates gammabutyrolactone, but the federal CSA does not). Even if narcotic drug in Penal Code 12021(a)(1) were defined by the shorter list of substances in Health & Safety Code 11019, the list is still overbroad since California punishes the possession of optical and geometric isomers; the CSA, in contrast, generally punishes the possession of optical isomers alone. Ruiz-Vidal, 473 F.3d at 1078 (citations omitted); see also Health & Safety Code 11019(b) (West 2007) (regulating isomer[s]). In short, the range of narcotic drugs covered by 12021(a)(1) is broader than that covered by the federal analogue 922(g)(3).

The statutes also differ in their definitions of use or addiction. The federal statute proscribes gun possession by any person . . . who is an unlawful user of or addicted to certain controlled substances. 18 U.S.C. 922(g)(3). Although some circuits read this phrase in the disjunctive, see, e.g., United States v. Bennett, 329 F.3d 769, 776 (10th Cir. 2003), the Ninth Circuit has consistently focused solely on the term unlawful user in analyzing convictions under 922(g)(3). See, e.g., United States v. Snipe, 515 F.3d 947, 954 (9th Cir. 2008); United States v. Purdy, 264 F.3d 809, 811-12 (2001); United States v. Ocegueda, 564 F.2d 1363, 1365 (9th Cir. 1977). Accordingly, to sustain a conviction under 922(g)(3), the Government must prove . . . that the defendant took drugs with regularity, over an extended period of time, and contemporaneously with his purchase or possession of a firearm. Purdy, 264 F.3d at 812-13 (emphasis added).

By contrast, the California statute proscribes gun possession by persons addicted to certain substances. Penal Code 12021(a)(1). The Supreme Court of California has held that for the Government to prove an individual is addicted to a substance, [t]he prosecutions burden is to show (1) that the defendant has become emotionally dependent on the drug in the sense that he experiences a compulsive need to continue its use, (2) that he has developed a tolerance to its effects and hence requires a larger and more potent does [sic], and (3) that he has become physically dependent so as to suffer withdrawal symptoms if he is deprived of his dosage. People v. ONeil, 401 P.2d 928, 932 (Cal. 1965); accord People v. Washington, 237 Cal.App.2d 59, 68 (1965). Unlike the federal definition of unlawful user, the California definition of addicted to does not contain the critical limiting requirement of contemporaneous use. See Purdy, 264 F.3d at 812-13. Hence, the California statute is broader because it does not require that the defendant use the drug at the time of his or her contact with the weapon, whereas the federal statute does demand the drug use to be contemporaneous with the possession of the firearm. Thanks to Thalassa Kingsnorth.