The Fourth Circuit has just held that Jose Padilla -- a U.S. citizen and alleged al Qaeda combatant who was captured in the U.S. -- can indeed be kept in military detention. In Hamdi v. Rumsfeld, the Supreme Court took this view as to Yaser Hamdi, a U.S. citizen and alleged al Qaeda combatant who was captured overseas. The question before the Fourth Circuit was whether the place where Padilla was captured should make a difference, and the Fourth Circuit said no. (The Court in Hamdi concluded that the military had to provide detainees some review procedure to determine whether they are indeed enemy combatants; but Padilla's challenge was apparently to the government's very power to detain him, and not to the process it has used to decide whether he's a combatant, see n.4 of the Fourth Circuit decision.)
So here's an interesting twist: The Hamdi decision rested on the votes of five Justices -- Rehnquist, O'Connor, Kennedy, Thomas, and crossover sensation Breyer; but in Rumsfeld v. Padilla, the dissent of Justices Stevens, Souter, Ginsburg, and Breyer opined that "American citizens arrested in the United States" could not be detained (at least for "protracted" times and "incommunicado"). Thus, it looks like Justice Breyer, the necessary fifth vote in the Hamdi precedent on which the Fourth Circuit relies, saw a distinction between detentions of U.S. citizens arrested in the U.S. and those arrested overseas, the very distinction that the Fourth Circuit quickly (and plausibly, given the reasoning of Hamdi) rejected.
I suspect that many lower courts would be reluctant to mix four Justices' views from one case (Hamdi) with one extra Justice's views in another (Padilla), especially when those views came in a footnote to a dissenting opinion written by another Justice (though, to be sure, an opinion that Justice Breyer did join without reservations). So in future cases involving Padilla . . . lower courts would be free to conclude that Padilla loses . . . .
This seems to have happened here: The Fourth Circuit followed the five Justices' view in Hamdi, and ignored Justice Breyer's endorsement of a limiting principle in the Padilla dissent. (Note, incidentally, that if Justice Breyer wanted to, he could have written a concurrence in the judgment in Hamdi that expressed the view that Hamdi was limited to U.S. citizens detained abroad. That would have affected the precedential weight of Hamdi; but his joining the dissent in Padilla didn't have that effect.)
But, as I also wrote, "What the Supreme Court will do with that, when and if Padilla's case comes back to the Justices, is impossible to tell." If the Court grants certiorari here, then Justice Breyer might well join Justices Stevens, Scalia, Souter, and Ginsburg -- the Hamdi dissenters -- in reversing the Fourth Circuit's decision.