Sylvia Longmire insists it wouldn't. Adam Ozimek counters:
Say the higher end estimate of marijuana revenues from the Rand corporation is correct, and legalizing would reduce cartel revenue by 26%, or that the 60% number is correct and they will make back an implausibly high 50% of their lost revenue in other activities. This means something like a 30% decrease in lost revenues. If this leads to a proportional decrease in long-run drug related murders in Mexico, then based on the 15,273 drug related deaths in 2010, there would be 4,580 fewer deaths each year. That's a huge gain in welfare even if it falls short of the quixotic goal of "killing the cartels". The end of alcohol prohibition in the U.S. did not mean an end to the mafia, but it did lead to a significant decline in murders and in their power. Longmire has not presented a convincing case that the same would not be true in Mexico.
The Dish 