Pretty sure it is the location because the atf regulates via the interstate commerce act. So once you have crossed a state line with a firearms purchase regardless of residency it falls under the above. Purchases are purchases and the feds say you cant buy a handgun out of state without going through a FFL. Might not be a problem in kentucky to purchase but is a problem when you cross any state line..... That's my guess, Im not a lawyer and more than likely incorect.
18 USC 922
Section 922. Unlawful acts
(a) It shall be unlawful -
(3) for any person, other than a licensed importer, licensed
manufacturer, licensed dealer, or licensed collector to transport
into or receive in the State where he resides (or if the person
is a corporation or other business entity, the State where it
maintains a place of business) any firearm purchased or otherwise
obtained by such person outside that State, except that this
paragraph
(A) shall not preclude any person who lawfully acquires
a firearm by bequest or intestate succession in a State other
than his State of residence from transporting the firearm into or
receiving it in that State, if it is lawful for such person to
purchase or possess such firearm in that State,
(B) shall not apply to the transportation or receipt of a firearm obtained in
conformity with subsection (b)(3) of this section, and
(C) shall
not apply to the transportation of any firearm acquired in any
State prior to the effective date of this chapter;
3A- Thats the awnser
