National Security Letters (NSLs) are an extraordinary search procedure that gives the FBI the power to compel the disclosure of customer records held by banks, telephone companies, Internet Service Providers, and others.
A National Security Letter is roughly comparable to an administrative subpoena. An NSL needs no prior judicial approval. Intelligence agencies issue them for intelligence gathering purposes to telephone companies, Internet service providers, consumer credit reporting agencies, banks, and other financial institutions, directing the recipients to turn over certain customer records and similar information. These entities are prohibited, or "gagged," from telling anyone about their receipt of the NSL, which makes oversight difficult. The Number of NSLs issued has grown dramatically since the Patriot Act expanded the FBI's authority to issue them.
Prior to the USA PATRIOT Act, the letters had to certify (1) that the information was relevant to a foreign counterintelligence investigation and (2) that specific and articulable facts gave reason to believe the information pertained to a foreign power or its agents.
Section 505 of the PATRIOT Act altered the FBI’s National Security Letter authority in several ways:
It expanded issuing authority to include the heads of FBI field offices (special agents in charge (SACs));
- It eliminated the requirement of specific and articulable facts demonstrating a nexus to a foreign power or its agents;
- It required instead that the information was sought for or relevant to various national security investigations; and
- It directed that no NSL related investigation of a “U.S. person” (American citizen or foreign resident alien) be predicated exclusively on First Amendment protected activities.
NSLs could be used to obtain information pertaining to individuals two, three, or more steps removed from the foreign power or agent of a foreign power that is the focus of the investigation.