With more states moving to legalize marijuana through ballot measures, and even more having medicinal marijuana laws on the books, many people may be confused about the legality of driving after using pot. While all states have laws prohibiting driving under the influence of alcohol or drugs, many people who live in states with medicinal marijuana laws think it's okay to get behind the wheel after using the substance.  But the truth is that no state that has legalized recreational marijuana use or medical marijuana permits people to drive under the influence. Just as alcohol is legal but driving drunk…