Cannabis legalization by states reduces illegal growing on US national forests

Abstract

Ten US states and the District of Columbia have legalized cannabis as of November 2018, and have adopted other policies regarding production, consumption, and the penalties associated with it. These policy changes may have affected illegal growing operations on national forests of the United States. Using data on the number of cannabis grow sites reported on 111 national forests between 2004 and 2016 together with information about state cannabis laws and when they were implemented, we find that recreational cannabis legalization is associated with decreased reports of illegal grow operations on national forests. Laws mandating minimum sentences for illegal cannabis possession or sales are associated with fewer reported grows, as is strict regulation of cannabinoid products. Taxes on sales have positive impacts on illegal growing, while law enforcement presence has a negative effect. Counterfactual simulations for 2016 quantify the magnitudes of these policy effects.