Joshua Marshall almost has this right:

Reading over the reportage of what happened yesterday, it seems clear that Luttig and the other two members of the panel were less perturbed about civil liberties issues per se (Luttig wrote the decision that allowed the government to hold Padilla indefinitely as an 'enemy combatant') than the administration's cynical willingness to jump from legal argument to legal argument, from one set of facts to another, as the needs of the moment dictate.

Cynical bastard that I am, I believe the motives behind the outrage were nearly as base as the Administration's. Luttig and his fellow Appellate Lords were pissed not about BushJustice's duplicity, but rather that the BushJustice wasted their time by making them hear and decide the case, all for nought. They didn't work so hard getting the ample duffs elevated to the appellate bench just to have to do more work. And they could have better spent the time taken to craft their original opinion writing Washington Post op-ed pieces demanding the end of civil liberties.