SINCE THE elimination of national origins quotas in 1965, the United States has been experiencing a new wave of mass immigration. The prolonged, stalemated debate that culminated in the passage of the Immigration Reform and Control Act of 1986 (IRCA) reflects a national consensus to curtail but not to halt this influx, which currently amounts to about 600,000 legal, and 100,000 to 300,000 or more illegal, immigrants each year.