Miller Doing Time While Novak Enjoys CNN

For those of you who read the New York Times, you probably know of the case involving Judith Miller, the Times reporter who has been sentenced to 18 months in prison for refusing to release her sources before a Federal Grand Jury.
What Miller did to receive a subpoena was miniscule: she gathered information relating to a case involving the syndicated columnist Robert Novak, who, during a rant about former U.S diplomat to various African nations, Joseph C. Wilson, disclosed that Wilson's wife, Valerie Plame, was a secret officer of the CIA, investigating weapons of mass destruction in Niger. Although what Novak did is grounds for a federal offense, since he not only ruined Plame's career as a secret agent but put her in immediate danger, no law enforcement authority seems interested in prosecuting him.
What's more interesting is that despite the possibility that a high level official might have leaked this information to Novak, he has not received a subpoena to testify. Furthermore, Judith Miller, who was merely reporting on the potential leak that may have occured in the Novak case, is now going to prison for contempt of court. What or who is protecting Novak from the wrath unleashed on the Miller?