Protection for Confidential Sources

In a comment over on TPMCafe, an individual going by the name of "hyperbolic pants" explains why the journalists whose testimony is being sought in the Valery Plame investigation are on particularly weak ground when they shield their sources:

Plame source wasn't communicating to a reporter about a crime. The Plame source was committing a crime by communicating to a reporter. That is an essential, significant difference. The act of communication itself was a crime.

Shielding the source in this case is damaging in two ways:
1. It is akin to having a murderer ask you to hold the victim's arms to keep them from flailing in self-defense. You may not be the murderer, but you are aiding and abetting. Think about it: who is the victim of this crime? The United States. By acting as passive participant in this crime (which is the act of communication itself), you make it impossible for the United States to defend itself from this crime, because...
2. You make it, ultimately, an unprosecutable crime. It would mean that the crime of this particular kind of communication would be absolutely and utterly unprosecutable if the other person involved happened to be a reporter. That's unacceptable.

The fact of the matter is, not even those accorded the greatest legal privacy protections -- clergy, attorneys, and mental health professionals -- are granted the right to be party to their clients' crimes. By committing a crime which takes the form of a piece of communication to a reporter, the source made the reporter a party to a crime, not just a person who happens to know about a crime.

Of course, as Joe Wilson points out, none of this debate would be necessary if it weren't for the irresponsible behavior of the White House.