Legal marijuana and crime reduction

The Guardian channels an academic paper from the EJ:

Here's the Guardian story:
Legal marijuana cuts violence says US study, as medical-use laws see crime fall
Murder and violent crime found to have decreased most in states bordering Mexico as drug cartels lose business to regulation

And here's the paper:

Is Legal Pot Crippling Mexican Drug Trafficking Organizations? The Effect of Medical Marijuana Laws on US Crime  

Evelina Gavrilova

Takuma Kamada

Floris Zoutman 

Forthcoming in Economic Journal 

Abstract: We examine the effects of medical marijuana laws (MMLs) on crime. We exploit theintroduction of MMLs as quasi-experimental variation. Using data from the UniformCrime Reports, we show that the introduction of MMLs lead to a decrease of 12.5 percentin violent crime, such as homicides, aggravated assaults and robberies in states that borderMexico. We also show that the reduction in violent crimes is strongest for counties closeto the border (less than 350km), while there is no significant impact of MMLs on crimefor counties located further inland. Analysis from the Supplementary Homicide Reportsdata reveals that the decrease in homicides can largely be attributed to a drop in drug-lawrelated homicides. We find evidence for spillover effects. When an inland state passesa MML, this results in a decrease in crime in the nearest border state. Our results areconsistent with the theory that the introduction of MMLs reduces activity by Mexicandrug trafficking organizations and their affiliated gangs in the border region. MMLs exposedrug trafficking organizations (DTOs) to legitimate competition, and substantially reducetheir profits in one of their most lucrative drug markets. This leads to a decrease in drug-related crime in the Mexican border area. Our results indicate that decriminalization ofthe production and distribution of drugs may lead to a reduction in violence in marketswhere organized drug criminals meet licit competition.