Governments have always tried to control their international trade. The General Agreement on Tariffs and Trade (GATT) came in to effect in 1948 and immediately led to concessions on lowering thousands of tariff barriers among the initial signatory countries. Goods officially leave the country when a government official called a customs officer has stamped a customs declaration and then sealed the shipment in some way. In the United States, the Department of Homeland Security, through its Transportation Safety Administration (TSA) and the Customs and Border Protection (CBP), has significantly increased its security procedures for air cargo shipments as a result of changes brought about by the attacks on September 11, 2001. Most freight harbors have areas where their shipping containers are docked until customs clearance, and international airports usually have areas referred to as bonded warehouses. These facilities are meant, however, to be short-term locations, not least because airport bonded warehouse fees can be prohibitively expensive.