A systematic review with a meta-analysis by the Campbell Collaboration and its update by the Australian Institute of Criminology compared results from 26 quantitative studies and found that policing focused on street-level drug sales points is effective to reduce drug-related crime, but there is no evidence that it reduces calls for service when it is not applied through proactive policing strategies. Traditional reactive policing is less effective for drug-related crime and not at all effective to reduce calls for service. In contrast, Problem-Oriented Policing (POP), hot spot policing, or community policing is effective in both cases. Geographically-targeted interventions are more effective to reduce drug offenses than generic interventions. Likewise, interventions that work on larger problematic areas are more effective to reduce drug offenses (but not calls for service) than approaches that focus on more restricted sites [1] [2].
A second systematic review, which identified 15 (methodologically less rigorous) studies that evaluated strategies focused on combating drug trafficking at street-level points of sale, suggests that an increased enforcement of drug laws by the police is unlikely to reduce drug market violence [3].