[The United States war against immigration. Paradoxical effects].

At the end of the 1950s, the United States permitted the entry of a half million Mexican migrants per year, of which 450.000 entered with temporary work visa and 50.000 as permanent residents. By the mid-1970s, however, changes in U.S. migration policy undertaken in the name of civil rights had eliminated temporary work visas and limited legal resident visas to 20.000 per year. With the opportunities for legal entry curtailed, migratory flows simply re-established themselves under undocumented auspices, giving rise to a chain reaction that culminated in a new war on immigrants and the unprecedented growth of the unauthorized population of the United States. The article shows that the rise of undocumented migration and the growth of America's undocumented population are a product of poorly conceived immigration and border policies.