A person not licensed under the Gun Control Act (GCA) and not prohibited from acquiring firearms may order a firearm from an out-of-state source and obtain the firearm if an arrangement is made with a licensed dealer in the purchaser's state of residence for the purchaser to obtain the firearm from the dealer.
[18 U.S.C 922(a)(3) and (5), 922(b)(3), 27 CFR 178.29]
The ATF's Code of Federal Regulations, Part 178 - Commerce in Firearms and Ammunition is available at the following link:
http://www.gpo.gov/fdsys/pkg/CFR-2000-title27-vol1/pdf/CFR-2000-title27-vol1-part178.pdf