'Making drugs legal' is frequently miss-understood. Treating addiction as a public health problem by decriminalising addicts and personal posession while keeping the trade in drugs firmly illegal, as in Portugal and now Norway, looks like the way to go.
The recent changes to the law in Norway are widely reported as 'decriminalising drugs'. That is highly misleading. They have decriminalised drug use and personal possession, but the drugs trade itself is still criminal.
There aren't black markets for things that aren't illegal. Often, the gang murders we thing of are "turf wars" where one gang is competing with another gang for the same sales territory.
So legalizing drug trade likely decreases drug gangs, which likely decreases murders. People might still die from drug use, but that becomes a separate problem.
Moonshiners started making it, and sometimes it created poison.
The police were corrupted where corruptible or killed when they didn't go the gangs ways.
The rich had parties and skirted the enforcement of the law.
I´m not sure if decriminalizing all drugs would change the equation much (there´s still smuggling, prostitution and other vices to lord over).
Are the homicides because of drug related issues? What about other drugs like cocaine and heroin?
80% of the crimes being linked to drug use means that most people will only care about the remaining 20%.
But, anyway, AFAIK, drug usage is not a crime in Brazil. Dealing is. And for dealing related crimes to go away, one has to legalize the entire production and distribution.
These stats, along with others, is the result of years of populism, corruption and neglect.
https://www.motherjones.com/environment/2016/02/lead-exposur...