The problem of Mexican workers emigrating to the United States is rooted in history. After the 1848 border treaty known as the "Treaty of Guadalupe" put an end to the war with the United States, reside= on the Mexican side of the border continued to cross it as they had always done. In 1942, during the Second World War, a US delegation negotiated permission for Mexican workers to be employed on the other side of the border in replacement of Americans in uniform. The agreements protecting Mexican workers" rights expired in December of 1964, and since then, only a limited number of workers, varying from year to year, has been allowed to cross the border. In fact, a larger number do enter the US: including so-called undocumented workers or "al...