• HISTORICAL CONTEXT
• FOCUS ON ILLEGAL ALIENS
• EMPLOYER RESPONSIBILITIES
• ECONOMIC AND SOCIAL DILEMMA
• FURTHER READING:

U.S. law defines an alien as any foreign-born person living in the United States who is neither a citizen nor a national. Since the concept of a "national," or one who owes allegiance to the U.S. government, is rather ambiguous, in practice aliens may be broadly construed as any noncitizen. Although many special categories exist under U.S. regulations, aliens can be classified in three broad classes: (I) permanent legal aliens, who are sometimes known as immigrants, (2) temporary legal aliens, also known as nonimmigrants, and (3) illegal aliens, also known as undocumented immigrants. Estimates for the...