File photo of a chalkboard with the current varieties of marijuana available for sale written on it at a medical marijuana center in Denver

 
File photo of a chalkboard with the current varieties of marijuana available for sale written on it at a medical marijuana center in Denver
The current varieties of marijuana available for sale are seen written on a chalkboard at a medical marijuana center in Denver in this April 2, 2012 file photo. The Rocky Mountain State already allows the use of marijuana for medical purposes such as severe pain relief, and some communities have embraced it enthusiastically. The prevalence of medical marijuana dispensaries in Denver has moved pot into the mainstream in Colorado's capital city, advocates and political leaders say. In Denver County, home to about 600,000 people, one in every 41 residents is a registered medical marijuana patient, leading to chuckles about the "Mile High City." REUTERS/Rick Wilking/Files (UNITED STATES - Tags: POLITICS DRUGS SOCIETY HEALTH)