There isn't one single answer to your question about reporters testifying in court. Here are the answers:
There is no federal "shield law" to protect reporters from revealing their sources if summoned to court and asked to do so under oath. Instead, all 50 states and D.C. are free to establish their own shield laws. Some have done so, some have not.
If the conversation with the reporter took place in a jurisdiction that has a shield law, and its terms apply to the present case, the reporter can refuse to answer such questions and suffer no consequences. If, however, there is no such a law in that place and or its terms do not cover this instance, the reporter MUST testify. If he/she refuses to answer the questions, he/she can be jailed indefinitely for "contempt of court." The last instance of the jailing of a reporter (for failure to reveal sources in a murder trial) took place in Texas two years ago, as I recall.
The reporters "privilege," where it exists, is like the spousal right not to testify against his wife or her husband. The government cannot force the testimony. However, the privilege can be waived, and the individual can CHOOSE to testify.
Based on all this, IMHO President Bush should make the following statement:
"This is a national security issue which is now shrouded in obscurity because those who know the facts are not talking. In these times, I would think that any person werking for the federal government AND any person working as a reporter to cover the federal government, would place the well-being of the United States above their own well-being."
"Therefore, as President and Commander in Chief I ask any federal employee with information about any conversations concerning the wife of Mr. Wilson, to come forward and state honestly what he or she knows. I also call on any reporters involved in any such conversation to come forward and state honestly what they know."
"I do not promise immunity from the law for anyone who comes forward. I do believe they should come forward, because the security of the United States is at issue."
That's my take on that situation, legally.
John / Billybob