I thought I was not smart enough to find the exact statue, but in Colorado it is illegal to be under the influence of alcohol and be in possession of a firearm. .04 is used for determining if someone is under the influence. DWI has it own rules. If they think you have been drinking and blow a .04 and are carrying,they will charge you with the offense. Now the specific statue, ... Again, CSP who got pulled over a few weeks ago was charged with not only DWI, but also under the influence and in possession of a firearm which is considered a prohibited use......
CRS- 18-12-106 Prohibited Use of a Weapon
(1) A person commits a class 2 misdemeanor if:
(a) He knowingly and unlawfully aims a firearm at another person; or
(b) Recklessly or with criminal negligence he discharges a firearm or shoots a bow and arrow; or
(c) He knowingly sets a loaded gun, trap, or device designed to cause an explosion upon being tripped or approached, and leaves it unattended by a competent person immediately present; or
(d) The person has in his or her possession a firearm while the person is under the influence of intoxicating liquor or of a controlled substance, as defined in section 12-22-303 (7), 18-12-105.1, as it existed prior to its repeal, or possession of a permit or a temporary emergency permit issued pursuant to part 2 of this article is no defense to a violation of this subsection (1).