This paper analyses the relationship between drug-related detentions for possession or petty dealing and drug-related violence. Two theoretical mechanisms are explored: (i) when a dealer is detained, the market is disrupted, and competition increases; (ii) when a consumer is detained, other consumers are deterred and seek new dealers, generating competition among groups and, consequently, increasing violence. These hypotheses are quantitatively evaluated using geocoded data from local San Luis Potosí, Mexico markets. Results suggest a relationship between drug-related violence and detentions occurring in a nearby location. These results emphasize the inefficacy of drug law enforcement strategies for reducing violence related to illegal drug markets in local settings and open the discussion for exploring different policies to reduce violence related to organized crime and the harms associated with illegal drug consumption.