The SELLER is in violation of 18 U.S.C. 922(a)(5), but I can't find a federal statute that puts the PURCHASER in violation.
Is the buyer in violation of 27 C.F.R. 478.29a?
Title 27: Alcohol, Tobacco and Firearms
PART 478—COMMERCE IN FIREARMS AND AMMUNITION
Subpart C—Administrative and Miscellaneous Provisions
§ 478.29a Acquisition of firearms by nonresidents.
No person, other than a licensed importer, licensed manufacturer, licensed dealer, or licensed collector, who does not reside in any State shall receive any firearms unless such receipt is for lawful sporting purposes.
[T.D. ATF–363, 60 FR 17451, Apr. 6, 1995]