The New York Times reports:

A federal judge dealt a setback on Friday to the Obama administration’s crackdown on the leaking of government secrets to journalists, sharply limiting what prosecutors can ask the author of a book about the C.I.A. in court.

Judge Leonie M. Brinkema of the Federal District Court in Alexandria, Va., issued an order that had been sought by the author, James Risen — who is also a reporter for The New York Times — restricting his testimony in the trial of a former Central Intelligence Agency official, Jeffrey A. Sterling, who is charged with providing classified information to Mr. Risen.

Specialists in media law portrayed the ruling as highly unusual, saying it could set an important precedent. While many states have so-called media shield laws that allow judges to quash subpoenas ordering reporters to testify about their sources by balancing the needs of prosecutors with the public interest, the federal government has no such statute.

“I think it’s an important victory for the First Amendment and for freedom of the press,” Mr. Risen said. “The protection of sources will allow for the American press to continue to find and report the truth.”

Federal prosecutors could appeal the judge’s decision. Alisa Finelli, a Justice Department spokeswoman, declined to comment on the ruling.

Prosecutors have charged Mr. Sterling with being a source for a chapter in Mr. Risen’s 2006 book, “State of War: The Secret History of the C.I.A. and the Bush Administration.” The chapter details an effort by the intelligence agency to sabotage Iranian nuclear research in 2000, portraying the operation as botched in a way that may have helped Iranian scientists gain valuable information about building a nuclear triggering device.