UPDATED: The Department of Justice said today it would appeal Wednesday's federal court ruling striking down a key provision of the Patriot Act. The provision in question authorizes the FBI to obtain sensitive customer records from Internet service providers (ISP) and other businesses without judicial oversight.

Judge Victor Marrero of the Southern District of New York struck down Section 505 of the Patriot Act on the grounds that it violates free speech rights under the First Amendment, as well as the right to be free from unreasonable searches under the Fourth Amendment.

"Under the mantle of secrecy, the self-preservation that ordinarily impels our government to censorship and secrecy may potentially be turned on ourselves as a weapon of self-destruction," Judge Marrero wrote in his 120-page decision.

The American Civil Liberties Union (ACLU), which brought the suit on behalf of an unnamed ISP, argued that the law was so broadly worded that it could be effectively used to obtain customer names from ISPs without a search warrant or subpoena.

"The New York district court has struck down as unconstitutional an important act of Congress, the 1986 National Security Letter statute," DOJ Public Affairs Director Mark Corralo said in a statement. "That decision takes away a tool for fighting terrorism that the Congress has authorized. The Department of Justice Department will appeal that decision."

The legal vehicle used by the FBI to obtain the names is known as a National Security Letter (NSL), which allows federal authorities to obtain names without a court order and bar Web sites and other firms from disclosing the inquiry to the customer, which is widely known as a "gag" provision. Before the Patriot Act, the FBI could use the NSL authority only against suspected terrorists and spies.

Judge Marrero's decision enjoins the government from issuing NSLs or from enforcing the gag provisions of the law. Marrero stayed the ruling for 90 days in order to allow the government an opportunity to raise objections in the district court or the Second Circuit Court of Appeals.

"This is a landmark victory against the Ashcroft Justice Department's misguided attempt to intrude into the lives of innocent Americans in the name of national security," Anthony D. Romero, ACLU executive director, said in a statement. "Even now, some in Congress are trying to pass additional intrusive law enforcement powers. This decision should put a halt to those efforts."

Prior to Wednesday's ruling, the ACLU was unable to disclose information about the case in order to avoid penalties for violating the NSL statute's broad gag provision. The ACLU contends the government "sought at every turn to censor even the most innocuous, non-sensitive information" about the case.

"After laboring under a gag provision for months, it is an enormous relief to be able to tell the world just how dangerous and extreme this Patriot Act power is," said ACLU Associate Legal Director Ann Beeson. "As the judge recognized, the Patriot Act imposed a 'categorical, perpetual and automatic' gag on every person who received a National Security Letter, as well as their lawyers."