The Wild and the Innocent

Making your own gun, whether the old fashioned way of doing custom metal work or using a 3D printer, is perfectly legal in the United States. In fact the ability to make and/or modify your own guns is a constitutionally protected right, a number of now famous guns were originally made by a gunsmith in their own house like Colt revolver or the Glock for a more modern example. It only becomes illegal when you sell the guns you make to other people without having a Federal Firearms License (FFL) or having a FFL dealer perform a background check, and even then when it comes to custom-made guns like 3D printed ones the law is ambiguous, it is still a gray area in many respects as these guns have no serial number and can't be traced. When buying a gun you are required to fill out ATF Form 4473, and one of the things the form requires is the make, model and serial number of the gun being purchased, and those are obviously things a homemade gun is not going to have, so even if you have a background check performed before selling a homemade gun you are not able to provide the information required by the ATF, hence the legal gray area.

The ATF agent describes the guns found in the van as "AK's", but none of them are. The guns in the crate are a mixture of M4/AR-15 carbines, P-90, MP-5 and Uzi sub-machine guns, none of them are AK-47's. An agent with the Bureau of Alcohol, Tobacco, Firearms and Explosives is supposed to be a firearms expert, that is not a rookie mistake they would make.