Mystifying

Maybe I'm just too dumb or too naive to understand the American justice system.
I just read that a U.S. Court of Appeals panel has unanimously ruled that Judith Miller of The New York Times and Matthew Cooper of Time Magazine must testify before a grand jury in connection with the leaking of information regarding the identity of undercover CIA operative Valerie Plame.
I'm not terribly surprised that the courts have ruled against freedom of the press. That is unfortunately quite common.
What I don't understand is how Robert Novak, who actually published the story that betrayed Ms. Plame's identity to the world, has managed to avoid being ordered to testify. And yet, two reporters who never wrote about Ms. Plame may go to jail for up to 18 months.
Is there some part of this story that I just don't understand? I have to believe that something is going on that either has escaped my understanding or the attentions of the press.
Has the press failed to provide a thorough analysis of this situation?n Or have I missed the articles that would make all of this clear to me?