“We show that the introduction of medical marijuana laws (MMLs) leads to a decrease in violent crime in states that border Mexico. The reduction in crime is strongest for counties close to the border (less than 350 kilometres) and for crimes that relate to drug trafficking. In addition, we find that MMLs in inland states lead to a reduction in crime in the nearest border state. Our results are consistent with the theory that decriminalisation of the production and distribution of marijuana leads to a reduction in violent crime in markets that are traditionally controlled by Mexican drug trafficking organisations.”   http://onlinelibrary.wiley.com/doi/10.1111/ecoj.12521/full

“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.” https://www.theguardian.com/world/2018/jan/14/legal-marijuana-medical-use-crime-rate-plummets-us-study

“Marijuana legalisation causing violent crime to fall in US states, study finds”  http://www.independent.co.uk/news/world/americas/medical-marijuana-legalisation-cannabis-us-states-violent-crime-drop-numbers-study-california-new-a8160311.html