The New York Times is bracing for another high-profile First Amendment confrontation after a federal judge in Virginia upheld an order compelling the newspaper to divulge its confidential sources for columns about the 2001 anthrax mailings.

The decision Tuesday by Judge Claude Hilton effectively places the Times in contempt of court, as attorneys for the newspaper have said it will not comply with any order to identify confidential sources.

The standoff stems from a libel lawsuit filed in 2004 by a former Army scientist, Steven Hatfill, who claimed he was defamed by five columns written in 2002 by Nicholas Kristof. Mr. Hatfill contended that the columns falsely fingered him as responsible for the anthrax mailings, which killed at least five people.

“We’re certainly disappointed,” Mr. Kristof told The New York Sun yesterday. “We certainly believe that it’s imperative not only for journalism but also for society as a whole that investigative reporting be allowed to use confidential sources.”

“Though it will make defending the case tougher, we are confident that, in the end, the columns will be vindicated,” a spokeswoman for the Times, Abbe Serphos, said.

Asked whether he was concerned about being jailed, Mr. Kristof said, “I understand that that is unlikely, but fundamentally, I care tremendously about being able to report and to offer people in government confidentiality for information and my fear is that, in general, in recent cases there been something of a shadow over our ability to do that.”

An attorney for Mr. Hatfill, Thomas Connolly, did not respond to messages seeking comment for this article.

Four of the columns in question did not include Mr. Hatfill’s name and referred to him simply as “Mr. Z.” After the attorney general, John Ashcroft, identified Mr. Hatfill as a “person of interest” in the anthrax probe, Mr. Kristof named him in a fifth column.

The scientist’s lawsuit asserts that the columns damaged his reputation and left him unemployable in his field.

While the FBI carried out searches of Mr. Hatfill’s home and a storage locker he rented, neither he nor anyone else has ever been charged with involvement in the anthrax attacks.

Judge Hilton’s ruling, which was not made public until yesterday, offered little insight into his reasoning. He simply indicated that a magistrate’s order forcing the disclosure of Mr. Kristof’s sources was “not clearly erroneous or contrary to law.”

In a more detailed ruling last month, the magistrate, Liam O’Grady, said there was no viable way for Mr. Hatfill to proceed with the libel suit without knowing the identities of Mr. Kristof’s sources. “The court understands the need for a reporter to be able to credibly pledge confidentiality to his sources,” Magistrate O’Grady wrote. “But that privilege must be balanced against the rights of a plaintiff.”

Legal filings in the case indicate that the dispute involves three sources to whom Mr. Kristof said he promised anonymity. Two of them were employees of the FBI, the columnist said in a deposition.

Judge Hilton’s early action on the case was favorable to the newspaper. In November 2004, the judge threw out the lawsuit, ruling that the Mr. Kristof’s columns were mainly critiques of the FBI and “are not reasonably read as accusing Hatfill of actually being the anthrax mailer.” The judge said dismissal of the case was “mandated by the First Amendment.”

Last year, a panel of the 4th Circuit Court of Appeals voted 2–1 to reinstate the suit. “A reasonable reader of Kristof’s columns likely would conclude that Hatfill was responsible for the anthrax mailings,” Judge Dennis Shedd wrote for the majority.

The Times sought review by the full bench of the appeals court and by the Supreme Court, but both turned down the case. Now the paper is expected to go to the same lengths to challenge the order to name its anonymous sources.

Mr. Hatfill has separate suits pending against the federal government over leaks to the press and against Reader’s Digest and Vanity Fair over articles about the anthrax probe.

In 2001, after the Boston Globe defied an order to identify confidential sources for a story about a chemotherapy overdose, a state court judge in Massachusetts ordered a default judgment in favor of a physician who sued the newspaper for libel. The Globe’s contempt resulted in a finding that it was liable for injuries it caused to the reputation of the doctor, Lois Ayash.