It has no deterrant effect. It is usually enforced in a discriminatory fashion. Drug Prohibition Drugs should be legalized. The money currently spent on the failed war on drugs should be spent on treatment programs. There is really no difference between drug prohibition now and alcohol prohibition.
Prohibition increases crime, reduces self-responsibility and increases governmental power.
Drug use is a victimless crime, and thus should not be punished. Indeed, the criminal drug laws protect drug traffickers from taxation, regulation and quality control. Those laws also support artificially high prices and assure that commercial disputes among drug dealers and their customers will be settled not in courts of law, but with automatic weapons in the streets. The U.S. government is trying to censor the Internet with The Communications Decency Act. Our current parental laws are arbitrary and overly draconian.