A new DUI law is in effect in Colorado which sets a legal limit for the amount of active THC in your system while driving. The legal limit is 5 nanograms per milliliter of blood. This law was fiercely debated with the main issue being that people metabolize THC at different rates and as a result, the amount of impairment varies drastically from person to person. Unlike alcohol, where if you are over 0.08 you are impaired, it's hard to determine if a person is impaired or not based upon THC levels alone. Out-of-state visitors can purchase, possess, and consume usa canada marijuana marijuana as well. The law makes no distinctions between Colorado residents and tourists possessing, purchasing, or consuming cannabis. Out-of-state visitors can purchase up to one ounce of cannabis as well from licensed retail dispensaries. Although marijuana is illegal federally, the government has stated they will not prosecute the possession or sale of marijuana, as long as state law is being followed, and those laws are “robust.”