Washington ? For the second time, a federal judge on Thursday struck down a Patriot Act provision that authorizes the FBI to demand, without court warrants, that phone companies, financial institutions and Internet providers secretly turn over records for use in national security investigations.

The ruling by U.S. District Judge Victor Marrero of New York, in a suit filed by the American Civil Liberties Union, marked another in a lengthening series of court actions nullifying key elements of the Bush administration’s counterterrorism strategy.

The FBI has said that National Security Letters, which are similar to subpoenas but require no court review, are an “indispensable investigative tool” in counterterrorism and counter-intelligence investigations.

The bureau uses the letters to obtain electronic records from phone companies, banks, credit card companies, Internet providers and libraries, saying such records frequently provide a basis for applications to a secret national security court for warrants authorizing secret searches or wiretaps.

The letters have sparked a growing controversy, however. In a lengthy report and in congressional testimony last spring, Justice Department Inspector General Glenn Fine found widespread and “troubling” abuses in the bureau’s issuance of 142,000 of the letters from 2003 to 2005, estimating that about 3,000 of the requests were probably illegal or improper.

Under the Patriot Act, the bureau or one of its field offices needs only declare that the information sought is “relevant” to a national security investigation in order to issue such a letter.

In 2004, Merrero struck down an earlier version of the law that authorized the bureau to send the letters, ruling that it violated the First and Fourth Amendments because it gave recipients no legal recourse and allowed the FBI to forbid recipients of the letters from disclosing their existence.

Congress attempted to address those concerns by revising the provision when it amended the Patriot Act in 2005. But the ACLU took issue with the new version of the gag order, as well, and returned to court in a “John Doe” suit on behalf of an unidentified Internet service provider.

Under the new provision, the recipient is barred from disclosing that the FBI “has sought or obtained access to information or records” if the FBI director or his agent certifies that the disclosure could create “a danger” to national security or to someone’s safety, or could interfere with an investigation or foreign relations.

The revised provision allows a federal judge to lift the gag order, but only if compliance “would be unreasonable, oppressive or otherwise unlawful.”

Marrero said the gag orders are an unconstitutional infringement on the recipients’ First Amendment rights. He said the FBI had withdrawn the National Security Letter in the case before the court, conceding that the information sought was no longer relevant to a terrorism investigation, but continues to assert that any disclosure of the letter would endanger national security.