Instead of decriminalization of marijuana let us do a massive education blitz on the dangers of marijuana use. This worked for me. When I was in high school we were all called to the auditorium to listen to a speaker.
He was a young man in a wheelchair. His legs were missing, he was blind and missing an arm. He explained how his condition was the end result of a decision to start smoking marijuana, and that he now planned to visit high schools to warn others of this dangerous way of life.
This was enough for me to never involve myself in this life-altering activity even though there were plenty of opportunities. Maybe more people could come forward and give their stories of the harm that drugs have caused them.
As the dangers are made more evident, (see how the dangers of smoking has decreased cigarette use) less people will be inclined to try the drug and with a lack of clients the grow-ops and criminal activity will have to slow down and, maybe, one day disappear.