Deterrence theory proposes that legal compliance is influenced by the anticipated risk of legal sanctions. This implies that changes in law will produce corresponding changes in behavior, but the marijuana decriminalization literature finds only fragmentary support for this prediction. But few studies have directly assessed the accuracy of citizens’ perceptions of legal sanctions. The heterogeneity in state statutory penalties for marijuana possession across the United States provides an opportunity to examine this issue. Using national survey data, we find that the percentages who believe they could be jailed for marijuana possession are quite similar in both states that have removed those penalties and those that have not. Our results help to clarify why statistical studies have found inconsistent support for an effect of decriminalization on marijuana possession.