This article is interesting.
[The debate over immigration policy in the United States has reached a crescendo in recent years, with particular concern over illegal workers and their impact on social well-being in this country. Yet in the prevailing analysis of this issue, the relationship between immigration and contemporary international trade policy is often overlooked. In particular, few commentators recognize or understand that a significant part of the surge in illegal labor from Mexico–the source of the majority of undocumented workers in the United States—stems from reforms that Mexico undertook in cooperation with the United States to liberalize trade flows across the Mexico-United States border.]
It goes on to say
[This Article seeks to elucidate that relationship by focusing on a particular example: agricultural production in Mexico, especially the production of corn, the staple crop of Mexican farmers. Since 1994, the following interrelationship between international trade rules, labor, and migration has unfolded across the Mexico-United States border: first, corn imports have surged into Mexico from the United States under import policy reforms brought about by the North American Free Trade Agreement (NAFTA) and related economic liberalizations in Mexico; and, second, displaced agricultural labor has migrated out of rural Mexico into Mexican cities, maquiladoras, and, not infrequently, the United States.]