In his post on yesterday's decision in (what I think we should all call) Hamdan II, Jack writes "The historical arguments for a conspiracy charge in military commissions under the laws of war, while not slam dunks, are . . . more powerful than similar arguments for material support." Thus, he "think[s] the strong suggestions of its death [that Ben and I separately offered] are premature . . . ."
Jack may well be right, but only if the government changes its position in al-Bahlul--the next military commission appeal pending in the D.C. Circuit, which raises the question whether a military commission has the power to try an individual for conspiracy based on pre-2006 conduct. [Disclosure: I coauthored an amicus brief on behalf of the National Institute for Military Justice in support of al-Bahlul in the D.C. Circuit.] The government's brief in the Court of Appeals, for example, focuses on a variation of the argument it offered with respect to material support in Hamdan II, i.e., that conspiracy has long been recognized as an offense triable by military commission under the "U.S. common law of war." Thus, if one reviews the heart of the government's case in al-Bahlul on this point, see pp. 39-47 of this PDF, one finds a host of U.S. domestic examples, and--unless I missed something--no citations whatsoever to any non-domestic authorities on customary international law.
Later in the government's brief in al-Bahlul, it responds to the ex post facto concerns raised in al-Bahlul's opening brief by conflating the U.S. common law of war with customary international law. Here's page 67:
The crimes for which Bahlul was convicted are traditional common law crimes, and “[t]he common law, in short, presupposes a measure of evolution that is incompatible with stringent application of ex post facto principles.” Rogers v. Tennessee, 532 U.S. 451, 461 (2001); cf. Trial of Altstötter, 6 L. Rep. Trials of War Criminals 1, 41 (1948) (“To have attempted to apply the ex post facto principle to judicial decisions of common international law would have been to strangle that law at birth.”); see also id. at 43 (“As applied in the field of international law that principle requires proof before conviction that the accused knew or should have known . . . that he would be subject to punishment if caught.”). Moreover, “[f]air warning does not require that the defendants understand that they could be subject to criminal prosecution in the United States so long as they would reasonably understand that their conduct was criminal and would subject them to prosecution somewhere.” United States v. Al-Kassar, 660 F.3d 108, 119 (2d Cir. 2011), cert. denied, No. 11-784 (May 14, 2012).
In other words, the government's evidence that conspiracy was an established offense is a host of scattershot domestic precedents (most of which the plurality rejected in Hamdan I), and its argument for why there is no ex post facto issue is because the EPF standard should be relaxed for "judicial decisions of common international law." Even if the latter point is correct (the Altstötter principle is hardly beyond criticism), it doesn't explain why the "U.S. common law of war" is synonymous with the "law of war" to which Congress referred in Article 21 of the UCMJ, 10 U.S.C. § 821--and Hamdan II specifically, and in my view convincingly, held that it is not.
Put another way, it seems to me that the government can only revive conspiracy as a viable military commission charge for pre-2006 conduct (and, as such, for any of the current Guantanamo detainees) by (1) convincing five Justices that the Hamdan I plurality and the Hamdan II panel both erred insofar as they concluded that 10 U.S.C. § 821 only incorporates customary international law, and not the "U.S. common law of war"; or (2) providing evidence that trying conspiracy in a military commission is, to quote Judge Kavanaugh, "based on norms firmly grounded in international law," as opposed to domestic practice. And to my mind, the government's brief in al-Bahlul doesn't do much on either of these fronts.
To be sure, it stands to reason that the al-Bahlul panel (Henderson, Rogers, & Tatel, JJ.) will now request supplemental briefing from the parties in light of Hamdan II. In light of the above analysis, such supplemental briefing will presumably focus on these two points. But one would think that if the government had the ability and/or the inclination to make either of these arguments, we would have seen them by now, no?