Jeffrey A. Miron, senior lecturer in economics at Harvard University, at CNN:
Prohibition creates violence because it drives the drug market underground. This means buyers and sellers cannot resolve their disputes with lawsuits, arbitration or advertising, so they resort to violence instead.
Violence was common in the alcohol industry when it was banned during Prohibition, but not before or after.
Violence is the norm in illicit gambling markets but not in legal ones. Violence is routine when prostitution is banned but not when it's permitted. Violence results from policies that create black markets, not from the characteristics of the good or activity in question.
The only way to reduce violence, therefore, is to legalize drugs. Fortuitously, legalization is the right policy for a slew of other reasons.
Prohibition of drugs corrupts politicians and law enforcement by putting police, prosecutors, judges and politicians in the position to threaten the profits of an illicit trade. This is why bribery, threats and kidnapping are common for prohibited industries but rare otherwise. Mexico's recent history illustrates this dramatically.
Prohibition erodes protections against unreasonable search and seizure because neither party to a drug transaction has an incentive to report the activity to the police. Thus, enforcement requires intrusive tactics such as warrantless searches or undercover buys. The victimless nature of this so-called crime also encourages police to engage in racial profiling.