"The employment of foreign workers as a supplement to the domestic labor force has been a recurrent public policy issue throughout much of the history of the United States. Under specific circumstances, nonimmigrant workers have been allowed legal access to the American labor market. They should not be confused with illegal immigrants who do not have such a privilege. The legislative and administrative actions that have authorized non-immigrant programs traditionally have been shrouded in controversy. Policy concerns have centered upon both the economic effects of non-immigrant workers on working conditions for citizen workers and the special restrictions often imposed on non-immigrants that would be considered unfair and often illegal if applied to citizen workers."
Available at: http://works.bepress.com/vernon_briggs/115/