In a paper published by The Economic Journal last month, a study by the Norwegian School of Economics in partnership with the Pennsylvania State University Department of Sociology and Criminology, found that marijuana legalization has led to a decrease in violent crime in U.S. states that border Mexico.

Over the past several years, sweeping reforms to marijuana policies have reached a tipping point with legal medical marijuana now in more states (currently 29) than those that continue to prohibit the sale and consumption of the plant for medical or recreational purposes.

The paper's authors say that not only is there a strong reduction in violent crime related to illegal drug trafficking in states and counties that border Mexico, but that when an inland state legalizes medical marijuana, there is a measurable reduction in violent drug trafficking crimes in the nearest border state:

"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 350km), 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."

The paper continues, "Our results are consistent with the theory that decriminalization 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."

To determine how marijuana legalization has affected traffickers, the researchers used data from the Uniform Crime Reporting Program, an FBI-maintained database. They found that medical marijuana laws have correlated with a 12.5 percent decrease in violent crime homicides, aggravated assaults, and robberies in states that border Mexico.

Cross referencing their findings with data from the FBI's Supplementary Homicide Reports, they found that the decrease in violent crime is largely due to a drop in drug-related homicides.

The findings are consistent with previous studies on the effects of marijuana legalization and violent crime. Denver experienced a 2.2 percent drop in violent crime rates the year after legal recreational marijuana first went on sale in the state of Colorado, and Denver property crime plummeted by significant 8.9 percent over the same period.

In Washington state where recreational marijuana was legalized in 2012, violent crime decreased by 10 percent overall from 2011 to 2014.

That hasn't stopped Trump Administration Attorney General Jeff Sessions from insisting this February that legalized marijuana results in higher violent crime, citing nameless "experts" and no statistics or studies to back up his claim:

"I don’t think America is going to be a better place when people of all ages, and particularly young people, are smoking pot. I believe it’s an unhealthy practice, and current levels of THC in marijuana are very high compared to what they were a few years ago, and we’re seeing real violence around that.

"Experts are telling me there’s more violence around marijuana than one would think and there’s big money involved."

Interestingly, Sessions attempted to support his assertion by reasoning that, "You can’t sue somebody for drug debt; the only way to get your money is through strong-arm tactics, and violence tends to follow that."

The very fact that commerce in marijuana remains in the black market, outside of the protections of the legal system, is exactly one reason why the sort of vigilante justice Sessions describes takes place.

RELATED ARTICLE: Congress Effectively Legalizes Medical Marijuana at the Federal Level

When marijuana is legalized, legitimate businesses engage in marijuana commerce, businesses run by law-abiding entrepreneurs with federal tax ID numbers and nothing to fear from turning to the courts to peacefully resolve disputes with vendors and customers.

In 2010, with the death toll from U.S. drug prohibition rising into the tens of thousands, I predicted on IVN that legalizing marijuana in the US would lead to a drop in violent crime:

"Any economist armed with basic microeconomic theory could explain how U.S. drug policies create the perverse incentives that have fueled the violence- and how to fix these policies to end the carnage.

"Legalizing marijuana in California would be a tremendous step in the right direction. Though it may seem counter-intuitive, economists understand that legalizing marijuana would greatly decrease its value and put an end to the violent drug cartel that currently profits from its sale (and uses those profits to secure future profits by purchasing arms and murdering competitors)."

I predicted that even legalizing marijuana in one state, California, would have a measurable impact in decreasing violent crime related to the black market drug trade. The latest Norwegian School of Economics study found that this is exactly what has happened.

Even just partial legalization of marijuana, for medical purposes only, in any single state, correlates with a measurable decrease in violent crime. For the remaining 21 states that have not yet eased the prohibition on marijuana, voters can save lives and end violence almost immediately by legalizing marijuana in their states.

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