Interoffice Memorandum: Revised National Security Adjudication and Reporting Requirements [open pdf - 98KB]
"U.S. Citizenship and Immigration Services (USCIS) conducts background checks on all applicants, petitioners, and beneficiaries seeking immigration benefits. This is done both to enhance national security and to ensure the integrity of the immigration process. USCIS has previously mandated that FBI [Federal Bureau of Investigation] name checks be completed and resolved before any positive adjudication can proceed on certain form types. This memorandum modifies existing guidance for applications where statutory immigration provisions allow for the detention and removal of an alien who is the subject of actionable information that is received from the FBI or other law enforcement agencies after approval of the application."
HQ 70/23 & 70128.1
U.S. Citizenship and Immigration Services: http://www.uscis.gov/