Legalize cocaine and watch the black market dry up. Nobody kills for the protection of their 'turf'. Dealers and kingpins no longer reel in such massive profits because the supply of their product is eased and isn't as lucrative as it used to be. Police will be able to concentrate on those who actually infringe upon the life, liberty and property of individuals rather than divert time, money and manpower away on those who only destroy themselves. Look, we've been through all of these arguments before when the topic was Prohibition.
Ah, ending alcohol prohibition got rid of all the gangs, turf wars and crime ...
It got rid of all those related to the illegal alcohol industry. Now we've got them for the illegal drug industry. Do you know that 70% of crime is drug related?