Originally Posted by A.Nonymous
Look at the null hypothesis of your statement. If we made meth and heroin legal tomorrow would we see usage go up, down or stay the same? If the answer is up, then having them illegal does cut down on usage even if it doesn't prevent it entirely.
Actually studies have shown that the legality of narcotics isn't a factor in an individuals decision to use or not.
I'll see if I can dig up the survey, but there was a study done of high school kids and the reasons they chose not to do drugs, rating them in importance and influence. Being illegal was last on the list after, family, friends, health, religion.