Immigration law determines whether a person is an alien, and sets the rights, duties, and obligations of being an alien in the United States. Immigration law also addresses how aliens gain residence or citizenship within the United States. Immigration law refers to the rules established by the federal government for determining who is allowed to enter the country, and for how long. Three federal agencies are charged with administering and enforcing immigration laws. Immigration and Customs Enforcement (ICE) investigates those who break the law, and prosecutes offenders. U.S. Citizenship and Immigration Services (USCIS) handles applications for legal immigration. Customs and Border Protection (CBP) is responsible for keeping the borders secure. All three agencies are part of the Department of Homeland Security. This practice area concerns itself with the individual and also with businesses seeking to bring in workers under a variety of visa programs and also with tourists who visit the islands under visa waiver programs. Foreign investment is a related practice area.