The FBI has lifted a gagging order against the non-profit Internet Archive after the organisation refused to hand over details on one of its users.

The Internet Archive, which stores web pages for posterity, received the request for information in November 2006.

When it refused the FBI issued a National Security Letter that forbade Internet Archive founder Brewster Kahle from talking to anyone about the case except his legal representation.

The case was so secret that other board members of the Internet Archive were not informed. However, Kahle decided to fight the case in the courts and the FBI has backed down.

"While it is never easy standing up to the government, particularly when I was barred from discussing it with anyone, I knew I had to challenge something that was clearly wrong," he said.

"I am grateful that I am able now to talk about what happened to me, so that other libraries can learn how they can fight back from these overreaching demands."

This is the third time that the FBI has backed down when a National Security Letter request has been challenged. The FBI has now said it will make the case public, but with identifying information on key staff removed.

"This is a great victory for the Internet Archive and the US Constitution," said Melissa Goodman, staff attorney at the American Civil Liberties Union, which helped to bring the case.

"It appears that every time a National Security Letter recipient has challenged it in court and forced the government to justify it, the government has ultimately withdrawn its demand for records.

"In the absence of much needed judicial oversight, and with recipients silenced and the public in the dark, there is nothing to stop the FBI from abusing its power."