The analysis uses data from the original 15 countries of the European Union, including repeated Eurobarometer surveys asking young people about substance use, regional-level Eurostat data, and national-level European Monitoring Centre for Drug and Drug Addiction data. The latter measures of legal culture surrounding substance use include enforcement and prosecution, treatment availability, and decriminalization. The results of multilevel models that account for the variation at all three levels show that legal culture does indeed affect young people’s substance use. For example, higher enforcement of low-level offenses results in higher last month marijuana use among young people, net of individual- and regional-level characteristics. In addition, higher levels of treatment within a country are associated with lower lifetime use of a drug other than marijuana. The models also indicate that local context matters, with net migration patterns, GDP growth, and population density affecting substance use. Both the findings concerning national policy and local factors remind us that a sociological account of legal culture and local contexts is crucial to understanding individual behavior.