From: https://www.atf.gov/content/firearms...censed-persons

Q: From whom may an unlicensed person acquire a firearm under the GCA?

A person may only acquire a firearm within the person’s own State, except that he or she may purchase or otherwise acquire a rifle or shotgun, in person, at a licensee’s premises in any State, provided the sale complies with State laws applicable in the State of sale and the State where the purchaser resides. A person may borrow or rent a firearm in any State for temporary use for lawful sporting purposes.

[18 U.S.C. 922(a)(3) and (5), 922(b)(3), 27 CFR 478.29 and 478.30]
Doesn't this mean there would have to be a CBI check due to Colorado's new gun laws?