Let's not be too quick to assume there was a single 'leaker'. Several leakers would give plausible deniability along the lines of 'How could you possibly think it was moi...you should check out ___'.
Do you know if they have to swear an oath? A legally binding 'under penalty of perjury' oath? If so, they should be prosecuted. Under any circumstance, this is the one time that GWB should name names and point fingers.
As I understand it, the Intelligence Committee members have to sign a document saying they will not divulge classified information. That is the reason Leaky Leahy was kicked off the Intel Committee -- he leaked classified information which was against the law but he was not removed back in the late 80's from the Senate and the people of Vermont didn't kick him out either!
I am trying to find if they truly do have to sign an oath or if that is just a rumor!