In 19 years on the federal bench, Judge Thomas Ellis III has ruled on a series of difficult cases involving free expression. In many instances, he has agonized publicly over his decision — and then proceeded to dismiss the First Amendment concern.

In the coming weeks, Judge Ellis, 66, is expected to preside over the trial of a case that has fit that pattern so far, the prosecution of two pro-Israel lobbyists for obtaining and conveying classified information to journalists and Israeli diplomats.

Last month, Judge Ellis declared that the advocacy work of the two former employees of the American Israel Public Affairs Committee, Steven Rosen and Keith Weissman, was “at the core of the First Amendment’s guarantees.” However, in a 68-page opinion, the judge went on to uphold the prosecution, which is breaking new ground by seeking to punish private citizens for disclosing classified information willingly furnished by a government official.

“Common sense and the relevant precedent point persuasively to the conclusion that the government can punish those outside of the government for the unauthorized receipt and deliberate retransmission of information relating to the national defense,” the judge, who sits in Alexandria, Va., wrote.

The decision distressed First Amendment advocates, who see little obstacle to similar charges against reporters.

“It is certainly one plausible reading of the law, but reading it as Judge Ellis does, and more importantly, reading it as the Department of Justice does, imperils not just these two former Aipac employees, but every journalist who writes about national security matters,” a First Amendment lawyer in Manhattan, Floyd Abrams, said. “It’s a deeply threatening case.”

Recently, the judge triggered what may be a more direct battle with the press by ordering the Justice Department to conduct an investigation of how CBS News learned about the Aipac probe in 2004. Journalists fear that the leak inquiry could turn into a chilling attempt to force CBS to disclose its confidential sources.

To some observers, Judge Ellis’s rulings in the Aipac case came as no surprise. During the murder and conspiracy case against the so-called American Taliban, John Walker Lindh, the judge ordered a freelance reporter for CNN, Robert Pelton, to testify about how he interviewed and videotaped the dazed Lindh in Afghanistan in 2001.The judge rejected arguments by Mr. Pelton that involving him in the trial could lead to attacks on journalists by terrorists and other marauders. “They don’t need excuses like that,” Judge Ellis said.

The Lindh case also led Judge Ellis to order another leak investigation, this one into who gave Newsweek internal Justice Department e-mails disclosing ethical concerns about interviewing Lindh without a defense attorney present. The Justice Department lawyer who released the information, Jesselyn Radack, claimed protection under a federal whistleblower law, but ultimately lost the law firm job she had taken after leaving the government and faced bar association ethics complaints.

Judge Ellis’s first major First Amendment case arrived just days after he took the bench in 1987. Like the Aipac case, the federal prosecution on obscenity charges of the owners of video stores and adult bookstores in Virginia broke new ground. The Justice Department, eager to follow through on the anti-pornography findings of a government commission, claimed that the stores were subject to confiscation as a racketeering enterprise.

The owners, Dennis and Barbara Pryba, protested that the most popular rentals at the video shops were of mainstream films, like Casablanca and the Wizard of Oz, and that the vast majority of the titles were not sexually explicit.

Judge Ellis struggled publicly with the question of seizing the entire business on the basis of about $100 worth of magazines and videos deemed obscene by a jury. “No matter how important the elimination of obscenity may be, the First Amendment cannot become a casualty,” he observed, according to an account in the Washington Post. He faulted Congress for an “astonishing” failure to think through the implications of using racketeering laws to protest obscenity. Despite his misgivings, the judge went on to confiscate the Prybas’ entire business and inventory and send Dennis Pryba to jail for three years.

“This judge has no sympathy for anyone,” Barbara Pryba said in an interview last week. “We were the test case. … They totally destroyed us.”

The Supreme Court turned aside the Prybas’ appeal, but in 1993, a divided court upheld the forfeiture tactic in a separate obscenity case.

“I know some people in the media bar are critical of Judge Ellis’s handling of these cases,” a Washington attorney, Terence Ross, said. “I’ve found him to be extraordinarily thoughtful about freedom-of-the-press issues. I don’t think anyone can say he hasn’t made those decisions in good faith after thinking carefully about the law and the facts. This is not some Rambo judge. Far from it.”

In another obscenity-related case, a lawyer filed with Judge Ellis a copy of Madonna’s book of nude photographs, “Sex.”The attorney noted that the work was atop the national best-seller list.

Judge Ellis said the book brought to mind H.L. Mencken’s comment that “no one ever went broke underestimating the taste of the American public.”

“After having perused the pages of ‘Sex,’ the court is persuaded that there is at least one obvious obscenity in this case: it is obscene that an individual could amass great wealth by purveying to the public such nonsense as ‘Sex,'” the judge wrote.

While unrepentant criminal defendants get little sympathy from Judge Ellis, defendants in libel cases seem to fare better. In 1992, the judge threw out a case against the Philadelphia Inquirer brought by a Virginia man who claimed the newspaper wrongly impugned his fund-raising efforts for gift packages for American soldiers overseas. And in 1999, Judge Ellis rejected a defamation claim brought by an automobile salesman over a disputed promotion involving free cars for players on the Washington Redskins.

Judge Ellis, who goes by the initials T.S. but is known to friends as Tim, was nominated by President Reagan at the urging of Senator Warner of Virginia, a Republican. The judge was confirmed by the Senate about a month later.

Born in Bogota, Colombia, where his American father was working, Judge Ellis attended Princeton and majored in aeronautical engineering. He served as a Navy pilot from 1961 to 1966 before going to Harvard Law School and a post-graduate year at Oxford.

An assistant to Judge Ellis said yesterday that he does not grant interviews.

The dean of William & Mary Law School, W. Taylor Reveley III, said Judge Ellis came to prominence while in private practice at a firm in Richmond, Hunton & Williams. He was part of a team handling the legal battle surrounding the attempt to open the Shoreham nuclear plant on Long Island. “It was an 18-ring circus,” Mr. Reveley, who was a managing partner at the firm, said in an interview. “Tim is extraordinarily smart and extraordinarily well committed to doing absolutely excellent work.”

Mr. Reveley said the young attorney gained a reputation for carefully preparing witnesses, often using chocolates to reward particularly good answers. “It was just amazing,” the law dean said.

Mr. Reveley said Judge Ellis was sometimes teased for one particular difficulty he had making the transition from military to civilian life. “Ellis, the great Navy jet pilot who could land on an aircraft carrier, was not nearly as skilled a pilot of an automobile,” the dean recalled. “On one occasion, his car was loaded up with a group of us and we ended up going way off an exit followed by a Suffolk County cop.”