Dude, he's already said he's stopping prosecuting legal mmj users in states that have such decriminalization laws. I guess it all just comes down to proper education and proof of concept. I saw a Law & Order as well as a Glee episode a few weeks ago when the news spread that they were advocating the use of mmj(well Glee didn't do it too well, kind of made fun of it). If I had to guess, this is just a trial run to see if there's any merit to decriminalizing/legalizing it and IF he does continue it will be later on in his term. Let's hope he does, afterall there's more non-violent mj users/dealers in prison than black people, at least in my state. Lol, not saying blacks should be arrested or anything.

http://www.nytimes.com/2009/03/19/us/19holder.html
House bill pushes Pennsylvania to go green, legalize marijuana - Pittsburgh Tribune-Review
Arizona Medical Marijuana Policy Project, Sponsors of 2010 Medical Marijuana
etc...