Sorry for the brevity of the diary, but it's a simple concept.
I think it would be fairly easy to get marijuana legalized, conceptually. However, it would require the cooperation of law enforcement in a couple different regions (although local police would work).
Step #1: Surprise searches of the dorms at Yale, Stanford, Harvard and Princeton. Arrest everyone in possession of marijuana.
Step #2: Watch as the rich and powerful move into action to make possession of marijuana perfectly legal, and something that doesn't even need to stay on any kind of criminal record.
Quick Note: I went to a very highly rated college. Tons of people there smoked pot. They are now the "leaders of industry" and whatnot. Had they been doing the same thing as poor black working class youth, they'd stand a good chance of being in jail.