A federal judge ruled Friday that the government can obtain records from the online social networking site Twitter in its criminal investigation of WikiLeaks.

Three key players in the probe had argued that handing over their Twitter account information violated their constitutional rights.

In a 20-page written opinion, U.S. Magistrate Judge Theresa Carroll Buchanan in Alexandria ruled that the information is not protected by the First Amendment because the Twitter clients have "already made their Twitter posts and associations publicly available." She also said they have "no Fourth Amendment privacy interest" in the release of their Internet protocol addresses because the government isn't seeking the content of their communication.

The case offered the first public insight into the government's criminal investigation of WikiLeaks founder Julian Assange and others suspected of disclosing thousands of classified documents on the anti-secrecy Web site.

The government had requested the trio's Twitter account information, including screen names, mailing addresses, telephone numbers, credit card and bank account information, and Internet protocol addresses.

Buchanan's ruling was a clear victory for the Justice Department.

Peter Carr, a spokesman for the U.S. attorney's office for the Eastern District of Virginia, said prosecutors had no comment. Twitter also had no comment.

The government has asked for personal Twitter account information from Assange; Bradley E. Manning, the Army private who is suspected of supplying classified material to the Web site; Birgitta Jonsdottir, a former WikiLeaks activist who is also a member of Iceland's Parliament; and two computer programmers, Rop Gonggrijp and Jacob Appelbaum. Jonsdottir, Gonggrijp and Appelbaum hired lawyers after Twitter informed them in January that their records were being sought.

Aden Fine, a lawyer with the American Civil Liberties Union who represents Jonsdottir, said they plan to appeal Buchanan's decision.

"The government should not be able to obtain information about individuals' Internet communications unless they withstand First Amendment scrutiny, and they didn't do that here," he said. "The government has asked for information about every single use of Twitter by our client, whether it is related to the government investigation or not, and we don't think the First Amendment permits that."