In the list of responsibilities of the Illinois Attorney General, we see:
Third ‑ To defend all actions and proceedings against any State officer, in his official capacity, in any of the courts of this State or the United States.
One must twist reality past the point where it screams in pain, in order to make a case that selling a government position for private profit is part of the "official capacity" of any government official. It requires a second torture session to demonstrate that a legislative body is a court. By contrast, I saw two other responsibilities (from that paragraph's list of 14) that don't need any torture at all to suggest, if (s)he believes Blagojevich is guilty, to ease the man out as smoothly as can be arranged.
By all accounts, though, Blagojevich's attorney has a habit of getting the guilty off. But you'd expect someone like Blagojevich to know the best defense attorney around, wouldn't you? One hopes the guy continues to confuse a legislature with a court, because they're much different critters, and the rules of one don't work in the other.