23 US states that have decriminalized marijuana1. Do you know that Massachusetts is one of the 23 US states that have decriminalized marijuana? It approved the medical marijuana bill on November 6, 2012, after getting 63% of the votes, and it was made effective on January 1, 2013.2. People who are suffering from certain types of illnesses may apply to be a part of the medical marijuana program. The diseases included in the approved list of medical conditions for medical marijuana ...