A US judge has ruled that the FBI cannot spy on people's internet and telephone use without a warrant.
Judge Victor Marrero, of the District of Columbia, determined that the rules under the Patriot Act that allowed the FBI to secretly request telephone, internet and email logs without applying for a warrant were barred by the constitution.
The Patriot Act was passed 43 days after the terrorist attacks in the US on 11 September 2001.
Judge Marrero found that the practice offended constitutional principles of checks and balances, and violated the guarantee of free speech.
In a 24-page summation the judge concluded that the government would also have to hand over evidence requested on under the Freedom of Information act or explain why it would not.
The case was brought by the American Civil Liberties Union, the National Security Archive and the Electronic Privacy Information Center.
"Today's ruling deals a blow to the administration's sweeping and often unfounded secrecy claims," said Nasrina Bargzie, an attorney with the National Security Project at the American Civil Liberties Union.
"When documents are withheld under the Freedom of Information Act, the government must have a better excuse for keeping the documents secret than 'because we said so'."
The judge found that the government's reasons for not releasing documents were "too vague and general" and that the FBI's justifications were "wholly inadequate".
The case will now go to the appeal courts and the government has until 12 October to respond.
