DAN GILLMOR is very unhappy with the detention of Al Muhajir, since he’s a U.S. citizen. I agree that that’s an important distinction.
If the U.S. government locks up noncitizens, it may be a human-rights violation (or it may not) but it’s not politically corrupting. When the government locks up citizens without following Constitutional niceties, it may tempt it to abuse that power, and it may intimidate critics by the threats of such abuse, both concerns that don’t exist when noncitizens are involved.
I think that’s a good reason for maintaining a firewall between treatment of citizens and noncitizens. One offers a risk (so far, based on Guantanamo, not realized) of human rights violations. The other offers a risk of tyranny, in which the government, which should be the servant of the people, begins to act as master. We’re not close to that yet, but we’re closer than we were.
UPDATE: Eugene Volokh identifies a World War Two case holding that citizens who join enemy belligerents can be imprisoned without trial for the duration of the war:
On the points made about the detention of the dirty bomber, I think this case is instructive: In re Territo, 156 F 2d 142 (9th Cir 1946), [which holds] that a citizen who is an enemy belligerent [there, a prisoner of war] can be held without trial for the duration of the war. The only question is whether the Executive’s determination of belligerent status is subject to habeas [corpus] review. I believe that it is, and should be, and I predict that the dirty bomber will seek habeas, and that the Executive will present its evidence, and that the federal courts will determine that he is in fact an enemy belligerent subject to detention without trial.