Immigration law determines whether a person is an alien, the rights, duties, and obligations associated with being an alien in the United States, and how aliens gain residence or citizenship within the United States. It also provides the means by which certain aliens can become legally naturalized citizens with full rights of citizenship. Immigration law serves as a gatekeeper for the border of the nation, determining who may enter, how long they may stay, and when they must leave. Immigration lawyers represent persons seeking temporary and permanent residency (green cards) status in the U.S., those interested in obtaining U.S. citizenship through a process called naturalization, and clients facing deportation and removal. Immigration attorneys may also represent businesses seeking to secure temporary visa status for foreign employees.