Also, although that may be the violence most prominent in the US, there's plenty of police/army vs. drug cartel violent crime in other countries.
edit: typo.
You can't go to a lawyer and say, "This dude backed out on his deal, cheating me out of $10,000 of grass."
So the only method left for many grey/black market areas is physical retaliation.
Outlaw a market, and only outlaws (and their own twisted senses of justice and retribution) will thrive in the market.
Precisely the point: If the cartels come to intimidate grandma, she calls the police, because her operation is legal and the intimidation is not. The police, because her operation is legal, then go after the cartel and shut them down.
Additionally, contract laws and theft/burglary laws and so on work in grandma's favor, because the legal system is at least potentially on the side of her legal operation. This alone greatly reduces the need for violence.
Hah, if it were that easy we wouldn't still be in this 'War on Drugs'.
Secondly, what is the violent side of drug activitey? Again my understanding is that it's mostly revolved around protecting/hiding illegal production, and moving the drugs to a dealer. If you eliminate that supply chain, that vector of violent activity would be cut off.
You've got this all mixed up. The violence is the competition. Drug violence is rarely about cartels vs cops -- more often it's cartels vs cartels and dealers vs dealers.