In the early part of the 20th century, many believed that banning alcohol sales would cure a number of social ills, but we found that people still abused alcohol, and because the revenue from illegal sales went to the worst elements of society rather than law-abiding businesses, we created new problems that were more severe than the ones we’d hoped to remedy. Eventually we realized that alcohol use wasn’t as problematic as having Al Capone-types running cities. For some reason we don’t see the analogy with respect to other substances whose use or abuse we think we can eliminate by law. We can’t, as the past 70 years or so have shown. It’s makes much more sense to de-criminalize marijuana use and regulate it as we do alcohol.