Time magazine reporter Matthew Cooper was been given the go-ahead by his source to reveal his or her identity to a grand jury, which will keep him out of jail.
New York Times reporter Judith Miller, by contrast, told a federal court in Washington she was still not testifying and will immediately serve jail time for as long as the grand jury meets.
Both were being asked to divulge information relating to their investigation of the leak of CIA employee Valerie Plame's name.
Time magazine had already given over records to the special prosecutor investigating the leak in hopes of keeping Cooper out of jail.
Bill Keller, managing editor of the New York Times, said people should feel a "chill" by the prosecutor's decision. "The choice [Miller] made is a brave and principled choice," he said.
First Amendment attorney Floyd Abrams said Miller joins a long list of journalists who refused to give up their confidential sources, stretching back to Benjamin Franklin's brother.
Abrams said that Miller did not consider that the source's release of Cooper from his confidentiality pledge was sufficient to release her from hers, saying it was a form that the source had signed after it was circulated by the administration asking for cooperation in the investigation.
Keller said Time's decision to give up documents may have helped Cooper get a "Get Out of Jail Free" card, but would not say whether it hurt Miller's chances of avoiding jail.
Miller has not been convicted of a crime but cited for civil contempt, so she could leave jail whenever she agrees to testify. Abrams did say that the judge could convert it from a civil contempt to a criminal contempt citation if he wanted to escalate the issue.
Abrams said Miller would not "violate her promise to her source" in order to get out of jail.
Cooper called it a sad day for the country. He said he had prepared a letter to the judge saying he would remain in civil contempt and go to jail, but that in a "stunning set of developments," that source agreed to give him a specific, personal and unambigouous waiver.
He said he agreed with Miller that the GI-issue waivers that sources had been asked to sign was coercive and not a legitimate waiver, but that his was different.
Cooper would not reveal the source to reporters or the content of the communication.
When asked whether Time giving up the notes, over his objections, forced his hand, Cooper said no. That it was only when he felt he had a release from the source.
Cooper called the development of the source waiver sudden and after he had already sent his son off to camp with a kiss and the caution that he might not see him for a while.
Saying Miller's jailing sends a "chilling message to all journalists and could suppress the flow of vital information to the public," Radio-Television News Directors Association President Barbara Cochran said: "We are calling on our members to contact members of Congress and ask them to support [federal shield law] legislation now pending in the House and Senate."
Abrams said he thought her jailing might also spur action on the bills.