I think this should be a pure states rights issue.
How about something along the lines of how abortion used to be-- each state can choose what they want. We all know what happened after a few decades... national legalization.
Also, considering that this is a gigantic industry which goes untaxed why couldn't we legalize marijuana, tax at 10%, and save our infrastructure. That would add a few 50 billion dollars a year into housing, education, health and social security. Or one month in Iraq.