National security letters are investigative tools used in foreign intelligence investigations to compel the disclosure of certain transactional information such as financial records and communications data.
NSLs have become controversial due to their increasing use by government agencies (primarily the FBI), and because of the non-disclosure requirements and the limited judicial oversight involved in their use.
A new report (pdf) from the Congressional Research Service sorts through the five statutes that authorize the use of National Security Letters, including the latest amendments which provide for a measure of judicial review.
An abbreviated version of the same report, without footnotes or appendices, is “National Security Letters in Foreign Intelligence Investigations: A Glimpse of the Legal Background and Recent Amendments” (pdf), March 21, 2006.
Administrative subpoenas used in criminal investigations are approximately analogous to national security letters used in foreign intelligence investigations. They are the subject of another new report from the Congressional Research Service.
For extended background on administrative subpoenas, see “Administrative Subpoenas in Criminal Investigations: A Brief Legal Analysis” (pdf), March 17, 2006.
An abbreviated version of that report is “Administrative Subpoenas in Criminal Investigations: A Sketch” (pdf), March 17, 2006.
CRS does not make its publications directly available to the public. Copies of these reports were obtained by Secrecy News.