I took a stab at it yesterday. But it's definitely worth reading Goldy, who's been stabbing away at the various legal twists and turns far longer than I have. Here's his take at length, and here's a handy cheat-sheet on how he sees it:

McKenna is claiming broad discretionary powers that are defined neither in the constitution nor in statute. In the Goldmark case, he is claiming the discretion to withhold legal representation from a state officer. In the Seattle case, he is claiming the discretion to affirmatively exercise powers beyond those duties proscribed by statute. Essentially, McKenna is claiming common law powers that he does not have.

More after today's hearing.