National Security Letters
An NSL is a subpoena issued by the FBI without judicial involvement for records relevant to terrorism or clandestine intelligence. The PATRIOT Act expanded their use into the tens of thousands. Recipients can petition a court and, since reforms, may disclose receipt; indefinite secrecy was replaced by presumptive termination.
An National security letter (NSL) is a subpoena that, before the PATRIOT Act, was used narrowly and only with FBI headquarters approval. The PATRIOT Act expanded NSL use into the tens of thousands per year, most involving U.S. citizens' records. Separate statutory provisions govern access to communication providers, financial institutions, consumer credit agencies, and travel agencies.
NSLs can be issued by authorized officials (often the special agent in charge of an FBI field office) without judicial involvement. Under the 2006 amendments, recipients can petition a federal court to modify or set aside an NSL if compliance would be unreasonable or oppressive, and the confidentiality (gag) requirement now applies only on an agency finding of interference with an investigation or other listed purpose. Recipients may disclose to those needed to comply and to an attorney. Breach of confidentiality can mean up to five years imprisonment and fines up to $250,000 for an individual.
Indefinite NSL secrecy ended: as of 2015 the FBI presumptively terminates secrecy when an investigation closes, or no more than three years after a full investigation opens.