Firearms will be transported between licensed importers, licensed manufacturers, licensed dealers and licensed collectors, as defined in the United States Gun Control Act of 1968 (Public Law 90-618, enacted October 22, 1968), as amended by the Firearms Owners' Protection Act (P.L. 99-308, approved May 19, 1986, and a subsequent amendment thereto, P.L. 99-360, approved July 8, 1986) ("the Acts"), law enforcement agencies of the United States or of any department or agency thereof, and law enforcement agencies of any State or any department, agency or political subdivision thereof,
and between persons not otherwise prohibited from shipping firearms by federal, state or local law and when such shipment complies with all applicable federal, state and local laws. The shipper must affix a UPS label requesting an adult signature upon delivery to each package containing a firearm. Adult means a person 21 years of age or older. UPS, in its sole discretion, may require the shipper to select a UPS Next Day Air Service for any shipment containing a firearm. Handguns, as defined by the Acts, will only be accepted for transportation via UPS Next Day Air Services, but will not be accepted for transportation via UPS Drop Boxes, Internet Shipping, or in response to a request for On-Call Pickup Service. Firearms, including handguns, will not be accepted when presented for shipment at locations of The UPS Store® or any Third Party Retailer (as described in Item 1090). Small arms ammunition, as defined in 49 C.F.R. § 173.59, will be transported only when packaged and labeled in compliance with 49 C.F.R. § 172.
http://www.ups.com/media/en/us_tariff_11012006.pdf