David Freddoso, writing for Culture11, defends the war on drugs:
The most tempting and most flawed argument suggests that drug legalization can free us from drug violence. Drug violence, we are told, is mostly the result of the legal ban on drugs. Eliminate the ban, and drug prices plummet. The financial incentive for violence vanishes. A legal trade in narcotics brings daylight to a black market. As an additional benefit, it eliminates the need to incarcerate so many drug criminals.
This argument is at least prima facie credible. Laws make criminals and illegal markets attract lawlessness. Disputes in the drug trade are settled through violent, extra-legal means because there exists no legitimate authority to enforce drug contracts, set industry standards or guarantee fair business practices in drug deals. Transactions are, as a rule, designed to be untraceable.
Posted by Mayo 
