The liberalization of cannabis policies is rapidly changing the cannabis industry. Though cannabis cultivation has environmental effects, little is known about how drug policy shapes knowledge about and efforts to mitigate those effects. We use a study of cannabis in the North Coastal Basin of California to examine how the legal status of cannabis shapes efforts to study and govern the environmental effects of cultivation. Drawing on interviews, a review of relevant rules and regulations, and existing literature, we review the state of the knowledge regarding the environmental effects of outdoor cannabis cultivation, document the range of governance tools that aim to mitigate those effects, and discuss the unique challenges to researching and governing cannabis cultivation. We argue that the quasi-legal status of cannabis and the mixing of black and medical markets create substantial barriers to the assessment and mitigation of the environmental effects of cannabis cultivation. We discuss the policy implications of these findings and highlight the importance of understanding the linkages between other semi-legal and illicit practices, governance, and the environment. The research shows the broad importance of examining ways that legal status and enforcement regimes surrounding semi-legal activities shape particular human-environment interactions.