National Security Letters in Foreign Intelligence Investigations: Legal Background [January 3, 2014] [open pdf - 502KB]
"Five federal statutes authorize intelligence officials to request certain business record information in connection with national security investigations. The authority to issue these national security letters (NSLs) is comparable to the authority to issue administrative subpoenas. The USA PATRIOT Act […] expanded the authority under four of the NSL statutes and created the fifth. Thereafter, the authority has been reported to have been widely used. Prospects of its continued use dimmed, however, after two lower federal courts held that the lack of judicial review and the absolute confidentiality requirements in one of the statutes rendered it constitutionally suspect. A report by the Department of Justice's Inspector General (IG) found that in its pre-amendment use of expanded USA PATRIOT Act authority the FBI had 'used NSLs in violation of applicable NSL statutes, Attorney General Guidelines, and internal FBI policies,' but that no criminal laws had been broken. A year later, a second IG report confirmed the findings of the first, and noted the corrective measures taken in response. A third IG report, critical of the FBI's use of exigent letters and informal NSL alternatives, noted that the practice had been stopped and related problems addressed."
CRS Report for Congress, RL33320
Federation of American Scientists: http://www.fas.org/sgp/crs/index.html