The United States Immigration and Naturalization Service (INS) was an agency of the U.S. Department of Justice from 1933 to 2003.Referred to by some as former INS and by others as legacy INS, the agency ceased to exist under that name on March 1, 2003, when most of its functions were transferred to three new entities – U.S. Citizenship and Immigration Services (USCIS), U.S. Immigration and Customs Enforcement (ICE), and U.S.