Ritter's move comes after Colorado Attorney John Suthers concluded in an opinion issued Monday that medical marijuana is considered personal property that can be taxed and shouldn't be treated like prescription drugs, which are tax exempt.

Ritter spokesman Evan Dreyer says the administration will immediately tell dispensaries to get retail licenses and start paying sales tax, The Denver Post reports.

Colorado lawmakers estimate the state could collect up to $15 million a year on the sales.

The decision comes just as Denver moves to impose sales tax on medical marijuana. Denver plans to notify dispensaries that it will start collecting municipal sales tax starting in December.