U.S. District Judge Thomas Hogan ordered Miller jailed until she agrees to testify about her sources before a federal grand jury, but said she could remain free while seeking an appeal. Miller could be jailed up to 18 months.
Hogan cited Supreme Court rulings that reporters do not have absolute First Amendment protection from testifying about confidential sources.
He said there was ample evidence that U.S. Attorney Patrick Fitzgerald of Chicago, the special prosecutor heading the CIA leak case, had exhausted other avenues of obtaining key testimony before issuing subpoenas to Miller and other reporters.
"The special counsel has made a limited, deferential approach to the press in this matter," Hogan said. Miller's testimony "is necessary for completion of this investigation ... and is expected to constitute direct evidence of innocence or guilt," Hogan noted.
Hogan last month upheld a subpoena requiring Miller to testify, a decision consistent with his earlier rulings. In recent weeks, Hogan had rejected claims that the First Amendment protected several other journalists involved in this case from subpoenas.
Fitzgerald is investigating whether a crime was committed when someone leaked the identity of CIA officer Valerie Plame, whose name was published by syndicated columnist Robert Novak on July 14, 2003. Novak cited two "senior administration officials" as his sources.
The Novak column appeared after Plame's husband, former Ambassador Joseph Wilson, was critical in a newspaper opinion piece of President Bush's claim that Iraq sought to obtain uranium in Niger. The CIA had sent Wilson to Niger to investigate that claim, which he concluded was unfounded.
Miller's lawyer, Floyd Abrams, said he would immediately file an appeal of Hogan's ruling with the U.S. Court of Appeals for the D.C. Circuit. He and Miller both noted that although she gathered material for an article about Plame, she never wrote one.
"I think it's really frightening when journalists can be put in jail for doing their job effectively," Miller told reporters outside the courthouse.
"Confidential sources, especially in Washington, are vital for balanced reporting if the public is to hear from government critics," she said.
Fitzgerald also has issued subpoenas to reporters from NBC, Time magazine and The Washington Post. Some have agreed to provide limited testimony after their sources -- notably Lewis "Scooter" Libby, Vice President Cheney's chief of staff -- released them from their promise of confidentiality.
But Miller and New York Times executive editor Bill Keller said they would not agree to provide testimony even under those circumstances. The Times reportedly suspects that the Bush administration may have forced White House officials and others to sign the waivers, making them invalid. A source who did not voluntarily waive his right to keep his name private might sue the newspaper later for violating that agreement, Editor & Publisher reported Sept. 22.
Novak has not said whether he has been subpoenaed.