"A Customs bonded warehouse is a building or other secured area in which imported dutiable merchandise may be stored, manipulated, or undergo manufacturing operations without payment of duty for up to 5 years from the date of importation. Authority for establishing bonded warehouses is set forth in Title 19, United States Code (U.S.C.), section 1555. The regulations covered the operation of bonded warehouses is found at 19 CFR 19. Upon entry of goods into the warehouse, the warehouse proprietor incurs a liability for the merchandise under a warehouse bond. This liability is generally cancelled when the merchandise is: 1. Exported; 2. Withdrawn for supplies to a vessel or aircraft; 3. Destroyed under CBP supervisions; or 4. Withdrawn for consumption within the United States after payment of duty. "
U.S. Customs and Border Protection: http://www.cbp.gov/