The gag order prevented Kahle from discussing the case with the library's board of directors, staff, and even his wife, he said. "Gags don't seem to be necessary," he said. "Gagging librarians is horrendous."

Kahle's lawyers declined to talk about the nature of the FBI investigation or reveal the identity of the targeted user.

The NSL sent to the Internet Archive asked for a user's name, address, length of service, e-mail header information and activity logs. The FBI investigation was "relevant to an authorized investigation to protect against international terrorism or clandestine intelligence activities," according to the FBI letter.

The Internet Archive provided the FBI some information that was publicly available on the site, but could not comply with the FBI request because the site does not track user activity or record IP (Internet Protocol) addresses, said Kurt Opsahl, a senior staff attorney with the EFF. The site asks only for an unverified e-mail address when users register.

Opsahl responded to the NSL in December. In addition to telling the FBI that the Internet Archive does not collect most of the personal information it sought, Opsahl also told the agency the Internet Archive was challenging the NSL on constitutional grounds. The US District Court for the Southern District of New York found the NSL program unconstitutional in September 2004, with the gag orders a violation of the First Amendment rights to free speech, Opsahl noted. The judge in the case has delayed his order pending government appeal.

Congress also gave some protections from NSLs to libraries in 2006, Opsahl told the FBI.

In each of the three court challenges to the NSL program, the FBI has withdrawn the information demands, ACLU's Goodman said. "I think that calls into question how much the FBI needed the information in the first place and, frankly, whether the FBI needs this kind of sweeping and unchecked surveillance power," she said.