Please explain how that would be relevant in the course of a private buyer and seller from AZ to CO. I don’t see where any of it apply’s unless state law doesn’t allow. and from what I’ve looked at this was a legal purchase. Let me also add that it should be, without interference from either the state of federal governments.
18 USC 922(a)(3) prohibits anyone who is not a dealer from going to a state in which he does not reside, buying a gun, and transporting or having it shipped back to his state of residence. That is what I presume the filmmakers did. If you’re not willng to read the law yourself, I am not sure how my explaining it will convince you.