The documents are believed to be the first time the government has provided details of its so-called national security letters, which are used by the FBI to conduct electronic surveillance without the need for court approval.

The filing made public Monday was the result of an 11-year-old legal battle waged by Nicholas Merrill, founder of Calyx Internet Access, a hosted service provider, who refused to comply with a national security letter (NSL) he received in 2004.

Merrill told Reuters the release was significant "because the public deserves to know how the government is gathering information without warrants on Americans who are not even suspected of a crime."