Caffeine, the Law, and Me

I was talking with a non-coffee-drinking friend recently about having to bring caffeine with me when I travel. "Addict," he said. "Nuh uh," I responded brilliantly. But it turns out that caffeine is surprisingly healthy, definitely a drug, and truly potentially addictive.

Which makes you wonder: if caffeine is an enhancing drug, and it's legal, why aren't the others?