Carolyn D Hines 
National Security Letters [PDF ebook] 
Background and Issues. Volume 1

National Security Letters (NSL) are roughly comparable to administrative subpoenas. 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. This book and its corresponding volumes present an overview of the background and issues surrounding the use of National Security Letters, the Patriot Act and First Amendment implications.