Here's how he recounts it in his interview yesterday:
Now, if you'd look at it from the perspective of a senior government official, somebody like myself, who stood up and took the oath of office on January 20th of 01 and raised their right hand and said we're going to protect and defend the United States against all enemies foreign and domestic, this was exactly, exactly what was needed to do it.
Here's the actual oath:
I do solemnly swear (or affirm) that I will support and defend the Constitution of the United States against all enemies, foreign and domestic; that I will bear true faith and allegiance to the same; that I take this obligation freely, without any mental reservation or purpose of evasion; and that I will well and faithfully discharge the duties of the office on which I am about to enter: So help me God.
My italics, of course. Is Cheney's ultimate defense is that he didn't understand the oath he took?