Medical marijuana is now legal in 20 states and the District of Columbia. Of those states, Washington and Colorado have legalized marijuana for recreational use. Colorado's first retail marijuana stores opened Jan. 1 for sale to people 21 years and older.
Under federal law, marijuana is still an illegal drug. However, the Justice Department is not challenging state marijuana laws as long as they don't conflict with eight federal enforcement priorities. These priorities include selling pot to minors, trafficking the drug and funneling marijuana revenue to gangs and cartels.