"The enactment of the Immigration Reform and Control Act of 1986 (IRCA) produced the most extensive legislation in the area of employment law in the United States in two decades (i.e., since the adoption of the Occupational Health and Safety Act of 1970). Its provisions affect every employer and every job seeker since the law went into effect on November 6, 1986. Among its multiple provisions were strictures designed to prohibit employers from hiring illegal immigrants. This action had the effect of repealing the 'Texas Proviso' of the Immigration and Nationality Act of 1952 that specifically exempted the employment relationship from constituting any charge of harboring illegal immigrants who were found on an employer's premises."
Available at: http://works.bepress.com/vernon_briggs/67/