On May 31, Ross Ulbricht lost his appeal with the Second Circuit appellate court. He will serve out the remainder of his life sentence, a sentence passed down in part due to allegations that he commissioned multiple murders-for-hire. Whether or not Ulbricht ordered these hits, his case illustrates how, by criminalizing drugs, the United States government has created an institution that incentives violence.

Ulbricht did not begin with violent intentions. He was an Eagle Scout who founded The Silk Road as a beacon of freedom. He agonized over the idea of a hit: As Wired reports, “He had talked to Inigo [an employee] about how he just wishes the best for people, and loves them in the libertarian spirit—even Green [Ulbricht’s first alleged target], in flagrante delicto.” But for Ulbricht and others involved in the drug industry, violence was in his self interest.

Opponents of drug prohibition argue that the drug industry is by nature violent. However, buying and selling drugs isn’t inherently more violent than is buying and selling alcohol. Rather, it’s black markets that create incentives for violence.

Black markets naturally attract criminals, in part because it’s difficult for convicted felons to find a career aboveboard. The black market for drugs offers lucrative opportunities that are especially attractive to those who have already committed violent crimes and are thus unlikely to find legal work.

Black markets also attract violent individuals because the crimes associated with selling drugs are proportionately less costly for those who already have a rap sheet. Legitimate businessmen are unlikely to sell drugs, because if they are caught they could face decades in prison. But for hardened criminals, the primary danger is in being caught, not in one more charge being added to an existing long list.

Additionally, black markets incentivize criminals to protect their secrecy. For many drug sellers, the most effective way to do so is to silence potential leaks. This was the context for Ulbricht’s first alleged hit: He feared that if his victim (an employee of The Silk Road) weren’t silenced, the employee might report Ulbricht’s crimes to the FBI. The difference between serving 10 years for drug trafficking and serving life for murder was a relatively small one compared to the difference between going to prison or remaining free.

Finally, black markets require violent dispute resolution. As Attorney General Jeff Sessions correctly argues, “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.” Faced with employees he suspected were cheating him, Ulbricht resorted to a seemingly violent resolution.

Ulbricht wasn’t attracted to illicit sales by his background, but once in the industry, his incentives pointed towards violence.

Violence is inherent in black markets, not theoretical: History makes a strong case that prohibition encourages aggression. When the 18th Amendment was passed, alcohol transitioned from a legitimate business to a funding source for organized crime. Violent crime increased dramatically as sellers went to extreme lengths to protect themselves and their stake. The 18th Amendment was passed in 1919, and homicides rose steadily from 1920 to 1933. Writing in American Law and Economics Review, Harvard Professor of Economics Jeffrey Miron argues that “drug and alcohol prohibition have substantially raised the homicide rate in the U.S. over much of the past 100 years.”

By contrast, when goods are legalized, crime declines. Legitimate businessmen replace Mafia gangsters, and entrepreneurs lose their incentive to kill in order to protect themselves. After the 21st Amendment ended Prohibition in 1933, homicides diminished for 11 years straight. Part of this was due to improving economic conditions, but part was likely also due to the fact that legal markets discourage violence.

The same trend can be seen with regards to medical marijuana. Writing in the Journal of Drug Issues, researchers analyzed violent and property crime in 11 Western states and found, “Significant drops in rates of violent crime associated with state MMLs [medical marijuana laws].” When drugs are legalized, violent crime declines.

Prohibition advocates argue that legalizing drugs might increase violent crime, as criminals move from the drug market into other illicit enterprises. This movement is plausible, but the net effect is still likely to be less crime. Prohibited substances fund criminal enterprises, and strangling this funding also strangles the organizations’ other activities.

Ulbricht began The Silk Road as a beacon of freedom and non-violence, but if reports about his activities are true, then he eventually embodied the violence of prohibition. Prohibition creates an incentive structure that encourages aggression. Black markets attract violent individuals, and move even decent people to brutality. If we want a safer and more peaceful world, we should learn a lesson from Ross Ulbricht and end the war on drugs.

Julian Adorney is a Young Voices Advocate and a FEE 2016 Thorpe Fellow. He currently works at Colorado SEO Pros. He’s written for a number of outlets, including National Review, the Federalist, the Hill, FEE, and Lawrence Reed’s latest anthology Excuse Me, Professor.