"In FY1995, the U.S. Border Patrol formally adopted a strategy known as 'prevention through deterrence.' This strategy calls for deploying Border Patrol agents directly on the border to deter illegal entry outright, rather than attempting to apprehend illegal aliens after they have entered the United States. Congress has supported expanding this strategy by providing the Border Patrol with greater finding and manpower. A key oversight issue for Congress is determining whether this strategy is effective in deterring illegal immigration. The U.S. Border Patrol's primary mission is to secure the 8,000 miles of land and water boundaries of the United States between ports of entry. The Border Patrol's major objectives are to prevent illegal entry into the United States, interdict drug smugglers and other criminals, and compel those persons seeking admission to present themselves legally at ports of entry for inspection. The Border Patrol is an enforcement division of the Immigration and Naturalization Service (INS)-the primary agency in the Department of Justice (DOJ) charged with administering the Immigration and Nationality Act (INA). In contrast to the Border Patrol's mission, INS Inspections and the U. S. Customs Service (a division of the Department of Treasury) share jurisdiction over ports of entry. INS Inspections is responsible for screening travelers seeking admission; the Customs Service is responsible for clearing the entry of goods and merchandise into the country. Under current law, both agencies are cross-designated to enforce each other's respective areas of the law. Further, inspectors from both agencies are cross-designated to enforce federal drug laws."
CRS Report for Congress, 97-989