The one thing about decriminalization is this...it's already begun in some states/cities. Sure the US Supreme court ruled it's illegal under any circumstances but they also ruled a slave was property. The court only rules, those rulings mean nothing if not enforced. Some cities/states (Alaska, what was it..detroit? or colorado or something, parts of California) all basically don't regulate or cite for small possession of it. They realize it's a waste of either jail space or tax payer money to try fight something so harmless.
Another good point was brought up regarding the differences between hemp and marijuana. Besides the # of leaves, marijuana is grown far apart to promote flowering/leaves whereas hemp is grown packed together to promote stock growth and little flowering/leave chutes. The main reason I bunch them together is that if it was re-legalized it would be senseless to have paid people to always inspect each growing site to verify that of those 100+ acres of hemp that not 1 was a marijuana plant. Instead they could do something like (for ever 1 marijuana plant 5 hemp plants must be grown) just to get some sort of regulation going on it while keeping it legal. Who knows though really...it's too much of a political suicide to talk about it so it'll take some time I bet and some slow but subtle changes for it to be legalized.