Michael C. Urziceanu (defendant) formed a cooperative that cultivated and distributed marijuana, and received client reimbursement for the cooperative's expenses. Urziceanu mistakenly interpreted California's Compassionate Use Act as permitting the cooperative to conduct these activities. The state (plaintiff) prosecuted Urziceanu for selling and conspiring to sell marijuana. The trial judge repeatedly refused Urziceanu's proffer of evidence that his actions were based on a good faith misreading of the statute, and denied Urziceanu's motions for a jury instruction on his mistake of law defense. The jury acquitted Urziceanu on the marijuana sales charge but convicted him on the conspiracy charge. Urziceanu appealed, arguing that his mistake of law constituted a defense to the conspiracy charge, because it negated his specific intent to violate the law.