Peter Margulies has a great post over at Lawfare on the fate of conspiracy as a crime punishable before military commissions. The D.C. Circuit recently ruled in Hamdan II that the crime of providing material support to terrorism could not be prosecuted before a military commission because it was not already a violation of the law of nations. The same argument regarding conspiracy is now ripe for review in the Bahlul case and will presumably reach the D.C. Circuit as well. How will the judges rule?
Margulies analyzes the fate of conspiracy and concludes that it might have a brighter future with the D.C. Circuit than material support. Whether this prediction comes true or not, one of the things that I like most about his analysis is that he takes great pains to distinguish between conspiracy as an inchoate offense and conspiracy as a mode of liability, and that the analysis might be different for each one. (For a different prediction, see Kevin Heller's post at Opinio Juris).
Conspiracy is a separate offense when it is charged as a distinct crime, and requires an agreement between two or more individuals to commit an unlawful act. As an inchoate offense, the crime to which the agreement is directed need not be completed for the conspirators to be guilty of conspiracy. The act of agreement itself is the inchoate crime of conspiracy. The inchoate crime gives prosecutors the advantage of early intervention in a burgeoning criminal endeavor, allowing them to charge individuals without having to wait for them to complete their criminal plan.
Conspiracy as a mode of liability is a way in which a crime can be perpetrated, and it provides a doctrinal avenue to establish the defendant's vicarious liability for the acts of his or her co-conspirators. Therefore, all conspirators are guilty of murder (or terrorism) just as much as the one conspirator who pulls the trigger or detonates the bomb. Consequently, conspiracy as a mode of liability requires someone to complete the underlying crime. Under the federal doctrine of Pinkerton liability, a co-conspirator may be held responsible for the acts of co-conspirators that fall outside the scope of the original agreement or plan, just as long as those wayward actions were reasonably foreseeable.
Now here's the relevance of this distinction. Conspiracy as an inchoate offense has been rejected in international criminal law, though there are pockets of uncertainty with regard to conspiracy to commit genocide, which is included in the Genocide Convention and the ICTY and ICTR Statutes (though excluded from the ICC Statute). But otherwise, conspiracy is disfavored. In his amicus brief before the Supreme Court in Hamdan I, George Fletcher referred to the inclusion of conspiracy to commit genocide in the ICTY and ICTR Statutes as the "afterglow of a dying concept". (See also my analysis of conspiracy to commit genocide in the OUP Genocide Convention Commentary here.)
However, conspiracy as a mode of liability is a more complicated business, as Peter Margulies rightly notes. There are a whole host of international doctrines that cover roughly the same ground as conspiracy, and might be functional analogues to conspiracy. The most notable is Joint Criminal Enterprise, whose third variant (JCE III) is exactly the same as Pinkerton liability (up to and including the requirement of reasonable foreseeability). Although the ICTY Appeals Chamber has consistently claimed that JCE and conspiracy are wholly distinct, I view them as roughly similar, since JCE liability allows a conviction for participating in a joint crime and requires an agreed upon plan or endeavor.
If and when the issue of conspiracy comes before the D.C. Circuit, I hope the judges take the time to untangle the two strands of conspiracy, and carefully consider in their analysis the other international doctrines that are roughly equivalent to conspiracy as a mode of liability.