associated with hostilities”.672 Both Acts specify that the military commissions have jurisdiction for offences committed before, on or after 11 September 2001.673 Additionally, these Acts stipulate that the provisions within them do not “establish new crimes that did not exist before the date[s]” of enactment.674 302. Under the MCA 2009, an alien “unprivileged enemy belligerent” is an individual who is not a US citizen and is not a privileged belligerent675 and who “(1) has engaged in hostilities676 against the United States or its coalition partners; (2) has purposefully and materially supported hostilities against the United States or its coalition partners; or (3) was a part of al Qaeda at the time of the alleged offense under this chapter.”677 The 2006 MCA used the term alien “unlawful enemy combatant”, which referred to an individual who (1) “engaged in hostilities or who purposefully and materially supported hostilities against the United States or its co-belligerents who is not a lawful enemy combatant” or (2) an individual whom the CSRT or other “competent tribunal” determined was an unlawful enemy combatant.678 303. The Ex Post Facto Clause of the US Constitution provides that “no (…) ex post facto Law shall be passed”.679 Although a court has not determined that this constitutional provision is applicable to Guantánamo detainees,680 the US government’s position is that the Ex Post Facto Clause does extend to them.681 The US Constitution also requires that penal statutes must explicitly define criminal offences so as to inform an average individual what conduct is prohibited and is subject to penalties.682 bodily injury, mutilating or maiming, murder in violation of the law of war, destruction of property in violation of the law of war, using treachery or perfidy, improperly using a flag of truce, improperly using a distinctive emblem, intentionally mistreating a dead body, rape, sexual assault or abuse, hijacking or hazarding a vessel or aircraft, terrorism, providing material support for terrorism, wrongfully aiding the enemy, spying, attempts to commit any of these offences, solicitation, contempt, perjury and obstruction of justice. MCA 2009, § 950t; MCA 2006, § 950v. 672 MCA 2009, § 950p. See, also, MCA 2006, § 948b(a). 673 MCA 2009, § 948d; MCA 2006, § 948d. 674 MCA 2009, § 950p(d); MCA 2006, § 950p. 675 A privileged belligerent is an “individual belonging to one of the eight categories enumerated in Article 4” of the Third Geneva Convention. MCA 2009, §§ 948a(6), 948c; RMC, Rule 202: “[m]ilitary commissions (…) shall not have jurisdiction over privileged belligerents”. 676 Hostilities are defined as “any conflict subject to the laws of war”. MCA 2009, § 948a(9). 677 MCA 2009, § 948a(7). 678 MCA 2006, § 948a(1). 679 US Constitution, Art. 1, § 9. 680 In this case, the US government conceded that the Ex Post Facto Clause did apply to detainees. The court assumed that the clause applied for the purpose of the case without definitively deciding its applicability. Five of the seven judges on the en banc court appeared to accept the applicability of the Ex Post Facto Clause to Guantánamo detainees (according to Judge Kavanaugh) on the basis of the United States Supreme Court ruling in Boumediene v. Bush. Two of the judges (Judge Henderson and Judge Brown) argued in separate opinions that the Ex Post Facto Clause does not apply to Guantánamo detainees. United States Court of Appeals for the District of Columbia Circuit, Ali Hamza Ahmad Suliman al Bahlul v. United States of America (en banc), Case No. 11-1324, 14 July 2014, <http://justsecurity.org/wp-content/uploads/2014/07/https___ecf.cadc_.uscourts.pdf>. 681 The US government confirmed that the US position is that the Ex Post Facto Clause is applicable to Guantánamo detainees. ODIHR meeting with Attorneys from the Departments of State, Justice and Defense, op. cit., note 193. 682 This is the Void for Vagueness Doctrine which stems from the due process clauses of the Fifth and Fourteenth Amendments. United States Supreme Court, Connally v. General Construction Co., Case No. 314, 4 January 1926, <https://supreme.justia.com/cases/federal/us/269/385/case.html>: “that the terms of a penal statute creating a new offense must be sufficiently explicit to inform those who are subject to it what conduct on their part will render them liable to its penalties (...) [a legislative provision] so vague that men of common intelligence must necessarily guess at its meaning and differ as to its application violates the first essential of due process of law.” 131