It wouldn't be nice for sure, but it would drastically slow down and change the magnitude. The thing is.. crime exists in most countries. What makes a big difference here is the amount of drug money coming into the cartels pockets, that type of money changes everything. We're talking of hundreds of billions of dollars a year, that's no pocket change. If money stops flowing in the cartels would have to switch to other types of operations, sadly still vicious and violent, but nothing like what they currently make.