Seeing my own words in print again, Ben, you're right, my question about criminal trials in federal courts came out a bit more gauntlet-y than I intended. Chalk it up to accumulated Guantanamo exhaustion. You've nonetheless given a good, thoughtful response, so let me offer a few quick reactions here (and figure we'll continue the discussion if not sooner at the American Constitution Society fiesta later this week).
On what existing options we have—your response seems to assume we've got federal courts or military commissions or nothing. That excludes the good old-fashioned court-martial, which I think many of us thought (at least I did and some JAGs I know) would have been just fine in cases where we needed to prosecute those picked up in Afghanistan or thereabouts. I'd still take the court-martial over the current military commissions any day: settled procedure (with room for discretion), trained participants, fair process, experienced in handling classified information, appeal to an established independent tribunal. You could perhaps still persuade me that despite all the water under the bridge, they might still work for a number of those we need to try at Guantanamo. You don't see the court-martial as an option at least for some?
On assessing how the federal courts have performed—you're quite right that simply saying they're better than the Guantanamo commissions is low praise, indeed. Too low, especially given the rather extraordinary degree of success prosecutors have had there. Instead, you say in response: It doesn't matter how well the courts have done in cases actually brought to trial, what really matters is how they would handle the whole universe of people we might ever want to detain—a universe you acknowledge is not well-defined but about which you are certain the federal courts aren't suited. Well, it would be great indeed if the administration would see fit to disclose a bit more about that whole universe of cases. In the meantime, it's hard to see how we can draw any conclusions about the federal courts' skills in that realm one way or another as long as, as you say, we don't actually have a handle on it.
More directly to your point, though, I do not argue that "the criminal law [is] the sole source of authority to detain people in the war on terrorism." Hard to know where to begin in citing my past comments on this, but you might take a look at a few of my briefs/writings here or here . The federal government has tons of detention authority beyond the (increasingly broad but still largely constitutional) criminal law—from immigration and civil commitment and material witness laws to, yes, battlefield detention under Congress' post-9/11 authorization for the use of force. Could be we disagree about the scope of the current "war," or the procedural limits the law of war imposes on executive power, but I'd be (and have been) the last to say the federal government shouldn't use its full range of lawful authority, all instruments of national power, etc., etc. in addressing the terrorist threat.
What I have suggested is that somewhere in all that existing detention power (all of which is currently supervised by existing judicial and administrative institutions), we might just already have what the detention universe demands. Now if I'm wrong about that, and the federal government needs more detention authority than it currently has, what we need isn't just (or particularly) a new court—we need a new statute authorizing the detention of some specific-enough-to-be-legal definition of others needing to be detained. But until the "new court" folks get down and dirty about who else, exactly, they want to detain, for how long, under what conditions, and why—then I can't figure how we know what kind of institution we need.