November, 2000 – Colorado voters consider and pass Amendment 20 to the state’s constitution, which legalized limited amounts of medical marijuana for registered patients and their primary caregivers.
October, 2009 – Deputy Attorney General David Ogden of the United States Attorney’s Office issues a memorandum stating that Department of Justice prosecutors “should not focus federal resources…on individuals whose actions are in clear and unambiguous compliance with existing state laws” as they relate to the medical use of marijuana.
June, 2010 – Colorado enacts the Colorado Medical Marijuana Code, which legalized and regulated marijuana dispensaries and created a regulatory framework for the licensing of patients and caregivers, as well as for the licensing of dispensaries. This provided an important structure and model for the eventual legalization of recreational marijuana by paving the way for dispensaries across the state.
November, 2012 – A majority of Colorado voters vote in favor of Amendment 64, which legalized recreational marijuana throughout the state.
May, 2013 – Governor Hickenlooper signs into law House Bill 1325, which allows law enforcement officers to infer a driver is impaired if the amount of THC in a person’s whole blood exceeds five (5) nanograms per milliliter.