I fought the law, and I won

Can somebody with more experience in Constitutional Law explain to me why Executive Privelege or Separation of Powers is being invoked to escape being called upon to testify (under oath, God forbid) before a congressional inquiry?
I mean, if Clinton had refused to meet with Ken Starr during HummerGate, or refused to allow cabinet members to do so, claiming that it would be inappropriate, certain political parties would have crucified him.

Seriously. How is G-Bu playing this avoidance of having testimonies, obviously important and relevant testimonies, being given or being given in private and not under oath?
Does he have a rational platform to stand on here, or is he just being the Chimpanzee in Chief again?

(no subject)

Grf. Nog appears to have gone tits up again.
Those Ellies to whom I owe email may have to wait.
I'll check again tomorrow morning and see if it's feeling any better but right now I'm off to bed.