Marijuana has been legal officially since 12/10/12, when Amendment 64 was passed. At that point it was legal to use or posess up to an ounce of the substance. The stores were actually commercially able to sell marijuana legally on January 1, 2014. Up until then it was also illegal to grow marijuana for commercial use. A person is only allowed to possess an ounce of marijuana at a time. Colorado residents can buy up to that amount, out-of-state purchasers may buy 3/4 oz.
Colorado amendment 64 made recreational marijuana legal on November 6th 2012. January 1st 2014 was the first day dispensaries opened up for business, prior to opening the first day, hundreds of people were waiting in line for these dispensaries to open up. A PTSD veteran was the first customer to purchase marijuana legally in Colorado.
The legalization of Marijuana in Colorado was voted on and passed November 6th, 2012. Throughout 2013, the Governor and state government officials had to come up with laws regulating the sales and determine tax rates. In September of 2013, they were able to finalize the new regulations and the legal sale of Marijuana started statewide on January 1st, 2014.