Border Security: Immigration Enforcement Between Ports of Entry

"[E]nhanced border enforcement may have contributed to a number of secondary costs and benefits. To the extent that border enforcement successfully deters illegal entries—an effect that is also difficult to measure since deterrence ultimately involves decisions made in towns and villages far away from U.S. borders—such enforcement may reduce border-area violence and migrant deaths, protect fragile border ecosystems, and improve the quality of life in border communities. But to the extent that aliens are not deterred, the concentration of enforcement resources on the border may increase border area violence and migrant deaths, encourage unauthorized migrants to find new ways to enter illegally and to remain in the United States for longer periods of time, damage border ecosystems, harm border-area businesses and the quality of life in border communities, and strain U.S. relations with Mexico and Canada." - CRS, Jan. 6, 2012.