¹ Koh, Harold Hongju & Buchwald, Todd F., The Crime of Aggression: The United States Perspective, 109 AJIL 257 (2015)Google Scholar.

² Rome Statute of the International Criminal Court, July 17, 1998, 2187 UNTS 90 [hereinafter Rome Statute]; International Criminal Court, Assembly of States Parties, Review Conference, The Crime of Aggression, ICC Res. RC/Res.6 (June 11, 2010) (adopting by consensus the “Amendments to the Rome Statute of the International Criminal Court on the crime of aggression,” contained in the resolution’s Appendix I). The resolution on the crime of aggression, as well as the other resolutions from the Kampala conference, is contained in the Review Conference’s Official - Records, ICC Doc. Rc/11 (2010). Part I includes the proceedings, and PartIithe resolutions, declarations, and various annexes. The Web page for the Assembly of States Parties, http://www.ICC-cpi.int/en_menus/asp/Pages/asp_home.aspx, provides access to all official records, general debates, and other records and documentation. The Rome Statute itself and other legal texts are available at http://www.ICC-cpi.int/en_menus/ICC/legal%20texts%20and%20tools/Pages/legal%20tools.aspx.

³ See ICC Res. RC/Res.6, supra note 2, Art. 15 bis(3) (“The Court shall exercise jurisdiction over the crime of aggression in accordance with this article, subject to a decision to be taken after 1 January 2017 by the same majority of States Parties as is required for the adoption of an amendment to the Statute.”

⁴ Un Charter, Art. 39 (“The Security Council shall determine the existence of any threat to the peace, breach of the peace, or act of aggression and shall make recommendations, or decide what measures shall be taken in accordance with Articles 41 and 42, to maintain or restore international peace and security.”).

⁵ Id., Art. 27(3) (“Decisions of the Security Council on all other matters shall be made by an affirmative vote of nine members including the concurring votes of the permanent members[.]”).

⁶ The “Amendments to the Elements of Crimes” are included as Annex Ii of ICC Resolution RC/Res.6, supra note 2 (“Article 8 bis... 3. The term ‘manifest’ is an objective qualification.”).

⁷ This issue identified here is different from the concern that the principle of complementarity will entitle states to undertake prosecutions of the crime of aggression. See Koh & Buchwald, supra note 1, at 273–77.

⁸ Carrie Mcdougall, The Crime of Aggression Under the Rome Statute of the International Criminal Court 14–15 (2015).

⁹ Un Charter, Art. 2(4) (“All Members shall refrain in their international relations from the threat or use of force against the territorial integrity or political independence of any state, or in any other manner inconsistent with the Purposes of the United Nations.”).

¹⁰ Definition of Aggression, GA Res. 3314 (XXIX) (Dec. 14, 1974). The resolution was adopted without a vote in the UN General Assembly, on the basis of consensus. The definition of aggression is an annex to the resolution.

¹¹ Yoram Dinstein, War, Aggression and Self-Defence 138–39 (5th ed. 2012).

¹² In particular, Article 8 bis reflects the language of Articles 1 and 3 of the resolution. For more on pre–Rome Conference approaches to defining the crime of aggression, see McDougal, Myers & Feliciano, Florentino, Legal Regulation of Resort to International Coercion: Aggression and Self-Defense in Policy Perspective, 68 Yale L. J. 1057, 1075–78 (1959)CrossRefGoogle Scholar.

¹³ Judicial Decisions: International Military Tribunal (Nuremberg): Judgement and Sentences, 41 AJIL 172, 186 (1947)Google Scholar (judgment of September 30, 1946); see also Kress, Claus, Time for Decision: Some Thoughts on the Immediate Future of the Crime of Aggression: A Reply to andreas Paulus, 20 Eur. J. Int’l L. 1129, 1138–39 (2009)CrossRefGoogle Scholar.

¹⁴ See GA Res. 380 (V) (Nov. 17, 1950) (passed by a vote of 50-5-1). Paragraph 1 reaffirmed, “any aggression... Is the gravest of all crimes against peace and security throughout the world.” But this statement begs the question as to the gravity of an act of aggression. See Kress, supra note 13, at 1137.

¹⁵ Koh & Buchwald, supra note 1, at 263–73.

¹⁶ Of course, the Preparatory Committee already noted this trend among states in its report containing the draft ICC statute. Report of the Preparatory Committee on the Establishment of an International Criminal Court at 14 n.15, UN Doc. A/CONF. 183/2 (Apr. 4, 1998) (“The proposal [on the crime of aggression] reflects the view held by a large number of delegations that the crime of aggression should be included in the Statute.”).

¹⁷ von Hebel, Herman & Robinson, Darryl, Crimes Within the Jurisdiction of the Court, in The International Criminal Court: The Making of the Rome Statute 79, 82 (Lee, Roy ed., 1999)Google Scholar.

¹⁸ Dinstein, supra note 11, at 140–56.

¹⁹ [1950] 2 Y.B. Int’l L. Comm. 376.

²⁰ The annex to the resolution is entitled “Declaration on Principles of International Law Concerning Friendly Relations and Co-operation Among States in Accordance with the Charter of the United Nations”.

²¹ This resolution states, “A war of aggression is a crime against international peace. Aggression gives rise to international responsibility.” There is, of course, room for “refining” or “clarifying” customary law. See Wilmshurst, Elizabeth, Definition of the Crime of Aggression: State Responsibility or Individual Criminal Responsibility?, in The International Criminal Court and the Crime of Aggression 93, 94 (Politi, Mauro & Nesi, Giuseppe eds., 2004)Google Scholar.

²² Cassese, Antonio, On Some Problematical Aspects of the Crime of Aggression, 20 Leiden J. Int’l L. 841, 847 (2007)Google Scholar.

²³ Danilenko, Gennady, ICC Statute and Third States, in 2 The Rome Statute of the International Criminal Court: A Commentary 1871, 1890–91 (Cassese, Antonio, Gaeta, Paola & Jones, John eds., 2002)Google Scholar.

²⁴ Cryer, Robert, Friman, Hakan, Robinson, Darryl & Wilmshurst, Elizabeth, An Introduction to International Law and Procedure 151–52 (2d ed. 2010)Google Scholar. This interpretation has been affirmed in Understanding 4 in ICC Resolution RC/Res.6, supra note 2. The “Understandings regarding the amendments to the Rome Statute of the International Criminal Court on the crime of aggression” are included as Annex Iii of the resolution.

²⁵ Kirsch, Philippe & Robinson, Darryl, Reaching Agreement at the Rome Conference, in 1 The Rome Statute of the International Criminal Court: A Commentary 67, 78–81 (Cassese, Antonio, Gaeta, Paola & Jones, John eds., 2002 Google Scholar).

²⁶ Koh & Buchwald, supra note 1, at 267.

²⁷ Id. at 265.

²⁸ GA Res. 3314 (XXIX), supra note 10, annex, Art. 4.

²⁹ McDougall, supra note 8, at 83–95. (“State practice and opinio juris are virtually non-existent.”); see also Ruys, Tom, ‘Armed Attack’ and Article 51 of the UN Charter: Evolutions in Customary Law and Practice 136–39 (2011)Google Scholar.

³⁰ Blokker, Niels, The Crime of Aggression and the United Nations Security Council, 20 Leiden J. Int’l L. 867, 880–81 (2007)Google Scholar. While the ICJ referenced the term in Armed Activities on the Territory of the Congo (Dem. Rep. Congo v. Uganda), 2005 ICJ Rep. 168, para. 146 (Dec. 19), and Military and Paramilitary Activities in and Against Nicaragua (Nicaragua v. U.S.), 1986 ICJ Rep. 14, para. 195 (June 27) (saying that Article 3(g) of the Definition of Aggression annexed to the resolution “may be taken to reflect customary law”), it is still not generally held to rise to the level of customary law status. See Dinstein, supra note 11, at 139.

³¹ Clark, Roger, Amendments to the Rome Statute of the International Criminal Court Considered at the First Review Conference on the Court, Kampala, 31 May–11 June, 2010, 2 Goettingen J. Int’l L. 689, 696 (2010)Google Scholar.

³² United Nations, Historical Review of Developments Relating to Aggression 225–37 (2003).

³³ This figure is current as of July 10, 2015. On the same date, the number of the parties to the Rome Statute stood at 123. See United Nations Treaty Collection, Chapter XVIII: Penal Matters, https://treaties.un.org/Pages/Treaties.aspx?id=18&subid=A&lang=en.

³⁴ Even at the stage of the Preparatory Commission for the ICC, Germany wanted the definition of aggression to be based in customary law. Proposal Submitted by Germany: The Crime of Aggression, PCNICC/2000/Wgca/Dp.4, para. 5 (Nov. 13, 2000).

³⁵ Koh & Buchwald, supra note 1, at 269–70.

³⁶ ICC Doc. RC/11, supra note 2, Annex IX(D) (“several serious concerns and questions over the definition of the act of aggression still remain, including the degree to which it may depart from customary international law, in particular as regards ‘act of aggression’”) (one of six “Statements by Observer States after the adoption of resolution RC/Res.6 on the crime of aggression”).

³⁷ Koh & Buchwald, supra note 1, at 264–69.

³⁸ This was clear in the run-up to the Kampala Review Conference. Murphy, Sean, Aggression, Legitimacy and the International Criminal Court, 20 Eur. J. Int’l L. 1147, 1155–56 (2009)CrossRefGoogle Scholar.

³⁹ Gray, Christine, International Law and the use of Force 18–19 (3d ed. 2008)Google Scholar.

⁴⁰ See, e.g., UN Charter, Arts. 10–14.

⁴¹ This role has also been recognized by the ICJ. Certain Expenses of the United Nations (Article 17, Paragraph 2, of the Charter), Advisory Opinion, 1962 ICJ Rep. 151, 163 (July 20).

⁴² Klein, Eckart & Schmahl, Stefanie, Article 12, in 1 The Charter of the United Nations 507, 514–16 (Simma, Bruno, Khan, Daniel-Erasmus, Nolte, Georg & Paulus, Andreas eds., 3d ed. 2012)Google Scholar.

⁴³ Schuster, Matthias, The Rome Statute and the Crime of Aggression: A Gordian Knot in Search of a Sword, 14 Crim. L.F. 1, 38 (2003)CrossRefGoogle Scholar.

⁴⁴ Military and Paramilitary Activities in and Against Nicaragua (Nicar. v. U.S.), 1984 ICJ Rep. 392, para. 95 (Nov. 26); see also United States Diplomatic and Consular Staff in Tehran (U.S. v. Iran), 1980 ICJ Rep. 3, para 40 (May 24).

⁴⁵ Blokker, supra note 30, at 885–86.

⁴⁶ “Where no such determination is made within six months after the date of notification, the Prosecutor may proceed with the investigation in respect of a crime of aggression, provided that the Pre-Trial Division has authorized the commencement of the investigation in respect of a crime of aggression in accordance with the procedure contained in article 15, and the Security Council has not decided otherwise in accordance with article 16.”

⁴⁷ “A determination of an act of aggression by an organ outside the Court shall be without prejudice to the Court’s own findings under this Statute.”

⁴⁸ Koh & Buchwald, supra note 1, at 266–68.

⁴⁹ Subject, as noted, to the Council’s deferral powers under Article 16 of the Rome Statute, supra note 2 (“No investigation or prosecution may be commenced or proceeded with under this Statute for a period of 12 months after the Security Council, in a resolution adopted under Chapter Vii of the Charter of the United Nations, has requested the Court to that effect; that request may be renewed by the Council under the same conditions.”). Although Article 34 of the Rome Statute states that the Court comprises several organs, including the Pre-trial Division and Office of the Prosecutor, it should be pointed out that the functions of the Court’s judicial divisions are to be carried out by chambers in accordance with Article 39(2)(a) and (b)(iii) of the Rome Statute, and that the same also applies in implementing the provision of Article 15 bis(8); the authorization for the prosecutor to investigate should be understood as coming from a pretrial chamber, as opposed to the Pre-trial Division (as suggested by the wording of the Article 15 bis(8)). Indeed, a straightforward reading of the Rome Statute makes clear that a pretrial chamber, not the Pre-trial Division as such, would be the source of any such authorization. For example, Article 82(1) and (2) mentions appeals only from a pretrial chamber. Likewise, the Rules of Procedure and Evidence—including Rule 50 (“Procedure for authorization by the Pre-Trial Chamber of the commencement of the investigation”)—make extensive reference to the role of a pretrial chamber, with no references to the Pre-trial Division. In any event, it is clear that the Kampala amendments envisioned the possibility that the Court, without direction from the Security Council, could authorize an investigation as requested by the prosecutor. See also Politi, Mauro, The ICC and the Crime of Aggression: A Dream That Came Through and the Reality Ahead, 10 J. Int’l Crim. Just. 267, 274–75 (2012)CrossRefGoogle Scholar.

⁵⁰ For this purpose, Article 121(3) of the Rome Statute, supra note 2, is the applicable provision; absent consensus, it requires a two-thirds majority of states parties.

⁵¹ Such jurisdiction could have otherwise been based on Article 12(2) of the Rome Statute, as the chapeau of Article 12(2) provides that “[i]n the case of article 13, paragraph (a) or (c), the Court may exercise its jurisdiction if one or more of the following States are Parties to this Statute or have accepted the jurisdiction of the Court in accordance with paragraph 3” (emphasis added). It means that nationals of a non-state party allegedly involved in a crime of aggression would be subject to the Court’s jurisdiction if the crime took place on a state party’s territory.

⁵² Wenaweser, Christian, Teaching the Kampala Compromise on Aggression: The Chair’s Perspective, 23 Leiden J. Int’l L. 883, 886–87 (2010)CrossRefGoogle Scholar.

⁵³ As noted earlier, the Understandings are included as Annex III of Resolution RC/Res.6, supra note 2. See also Kress, Claus, Barriga, Stefan, Grover, Leena & von Holtzendorff, Leonie, Negotiating the Understandings on the Crime of Aggression, in The Travaux Preparatoires of the Crime of Aggression 81–97 (Barriga, Stefan & Kress, Claus eds., 2012)Google Scholar.

⁵⁴ The Elements of Crimes, in comparison, has a standing on account of Articles 9 and 21(1)(a) of the Rome Statute, supra note 2, and is binding on the Court pursuant to Article 21(1)(a). Any amendment of the Elements of Crimes requires a two-thirds majority of the members of the Assembly of States Parties—an identical procedure to that for amending the statute. See also Cryer, Robert, Elements of Crimes (in the ICC), in The Oxford Companion to International Criminal Justice 308–09 (Cassese, Antonio ed., 2009)Google Scholar.

⁵⁵ Kress et al., supra note 53, at 91; see also Koh & Buchwald, supra note 1, at 272–73.

⁵⁶ Heller, Kevin Jon, The Uncertain Legal Status of the Aggression Understandings, 10 J. Int’l Crim. Just. 229, 245–46 (2012)CrossRefGoogle Scholar.

⁵⁷ Kaul, Hans-Peter, Kampala June 2010 —a First Review of the ICC Review Conference, 2 Goettingen J. Int’l L. 649, 665 (2010)Google Scholar.

⁵⁸ ICC Doc. RC/11, supra note 2, Annex Vii (statement by Japan before the adoption of RC/Res.6 by the Review Conference); id., Annex VIII(C) (statement by Japan after the adoption of RC/Res.6); see also Zimmermann, Andreas, Amending the Amendment Provisions of the Rome Statute, 10 J. Int’l Crim. Just. 209, 220–26 (2012)CrossRefGoogle Scholar.

⁵⁹ It may be noted that Article 39 remains the only provision of the UN Charter that employs the phrase “act of aggression.” The arguable implication is that only the Security Council can make a determination of an act of aggression under this provision in Chapter Vii of the Charter, but other interpretations are known to exist. See Mcdougall, supra note 8, at 269 (discussing that Article 15 bis (6) makes no reference to Chapter Vii).

⁶⁰ GA Res. 3314 (XXIX), supra note 10, para. 4; see also Krisch, Nico, Article 39, in 2 The Charter of the United Nations 1293, marginal note 43 (Simma, Bruno, Khan, Daniel-Erasmus, Nolte, Georg & Paulus, Andreas eds., 3d ed. 2012)Google Scholar.

⁶¹ Article 121(3) of the Rome Statute, supra note 2, allows amendments to be adopted by a two-thirds majority of states parties, absent consensus, at a review conference or meeting of the Assembly of States Parties.

⁶² Kirsten Sellars, Crimes Against Peace and International Law 286 (2013).

⁶³ ICC Doc. RC/11, supra note 2, Annex VIII(B).

⁶⁴ Id., Annex IX(F).

⁶⁵ The UN Security Council has not created a definition of its own. See McDougall, supra note 8, at 83.

⁶⁶ Contra Scheffer, David, The Complex Crime of Aggression Under the Rome Statute, 23 Leiden J. Int’l L. 897, 901 (2010)CrossRefGoogle Scholar.

⁶⁷ Article 2 of the definition of aggression annexed to Resolution 3314, supra note 10, provides (emphasis added (beginning with “although”)):

⁶⁸ Questions of Interpretation and Application of the 1971 Montreal Convention Arising from the Aerial Incident at Lockerbie (Libyan Arab Jamahiriya v. Uk), Provisional Measures, 1992 ICJ Rep. 3, para. 39 (Apr. 14).

⁶⁹ Un Charter, Arts. 108, 109.

⁷⁰ “[T]he use of armed force by a State against the sovereignty, territorial integrity or political independence of another State, or in any other manner inconsistent with the Charter of the United Nations.” Not so long ago, many states interested in the work of the International Law Commission in this respect were fully in support of the state character of the act of aggression. Olivier Corten, The Law Against War: The Prohibition on the use of Force in Contemporary International Law 187 (2012).

⁷¹ Likewise, the determination that an act of aggression has been committed is included as Element 3 of the crime of aggression under Resolution RC/Res.6, supra note 2: “The act of aggression—the use of armed force by a State against the sovereignty, territorial integrity or political independence of another State, or in any other manner in consistent with the Charter of the United Nations—was committed.”

⁷² Article 21(1)(b) of the Rome Statute, supra note 2, provides: “In the second place, where appropriate, applicable treaties and the principles and rules of international law, including the established principles of the international law of armed conflict[.]”

⁷³ Id., Arts. 1, 25. Under Resolution RC/Res.6, supra note 2, the new Article 25(3) bis provides: “In respect of the crime of aggression, the provisions of this article shall apply only to persons in a position effectively to exercise control over or to direct the political or military action of a State.”

⁷⁴ Cryer et al., supra note 24, at 332.

⁷⁵ Judicial Decisions, supra note 13, at 197–203 (finding a war of aggression against Poland).

⁷⁶ The parallel practice of the UN General Assembly under the UN Charter notwithstanding. Historical Review of Developments Relating to Aggression, supra note 32, at 242–51.

⁷⁷ See Security Council Resolutions 808 (Feb. 22, 1993) and 827 (May 25, 1993) (determining that the situation in the former Yugoslavia was “a threat to international peace and security”). See also Prosecutor v. Tadić, Case No. IT–94–1–AR72, Appeal on Jurisdiction (Oct. 2, 1995):

The question of whether the armed conflict in a given case was international or internal would be an ancillary matter, depending on the evidence of the case.

⁷⁸ For discussion of various calls for reform, focusing especially on the representativeness of the UN Security Council, see Fassbender, Bardo, Pressure for Security Council Reform, in The UN Security Council: From the Cold War to the 21st Century 341, 342–44 (Malone, David ed., 2004)Google Scholar. See also Report of the Secretary-General, Strengthening of the United Nations: An Agenda for Further Change, para. 20, UN Doc. A/57/387 (Sept. 9, 2002).

⁷⁹ Rome Statute, supra note 2, Arts. 39(2)(b)(iii), 57(2)(a). The latter provision requires that orders or rulings of the pretrial chamber under, among others, Article 15 “must be concurred in by a majority of its judges.” Accordingly, in such cases the pretrial chamber cannot comprise only a single judge. Article 15 bis is inserted after Article 15; its paragraph 8 requires compliance with the procedures laid down in Article 15.

⁸⁰ Un Charter, Art. 27(3).

⁸¹ Though representativeness in the context of the ICC may be evaluated based on inclusiveness of different legal systems, rather than geographical representativeness as emphasized in calls for Council reform.

⁸² Rome Statute, supra note 2, Art. 82(1)(d), (2). Article 82(2) allows appeal by leave of the pretrial chamber from that chamber’s decision to authorize the prosecutor, pursuant to Article 57(3)(d), to take specific investigative steps within the territory of a state party.

⁸³ United States Diplomatic and Consular Staff in Tehran (U.S. v. Iran), 1980 ICJ Rep. 3, para. 37 (May 24) (“legal disputes between sovereign States by their very nature are likely to occur in political contexts, and often form only one element in a wider and long-standing political dispute between the States concerned”). It is worth noting that the ICJ made the statement in light of the Iranian view that the violation of the diplomatic and consular law as alleged in the U.S. application was part of an “overall problem” between the two countries, involving “more than 25 years of continual interference by the United States in the internal affairs of Iran.” Id.

⁸⁴ James Crawford, The International Law Commission’S Articles on State Responsibility: Introduction, Text and Commentaries 16–20, 36 (2002).

⁸⁵ Koh & Buchwald, supra note 1; see also Koh, Harold H., International Criminal Justice 5.0, 38 Yale J. Int’l L. 525, 537 (2013)Google Scholar.

⁸⁶ Rome Statute, supra note 2, Art. 16 (“No investigation or prosecution may be commenced or proceeded with under this Statute for a period of 12 months after the Security Council, in a resolution adopted under Chapter Vii of the Charter of the United Nations, has requested the Court to that effect; that request may be renewed by the Council under the same conditions.”).

⁸⁷ Paulus, Andreas, Second Thoughts on the Crime of Aggression, 20 Eur. J. Int’l L. 1117, 1125 (2009)CrossRefGoogle Scholar.

⁸⁸ Koh & Buchwald, supra note 1, at 267 (on terrorism and cyber warfare).

⁸⁹ This point relates to the Rome Statute’s overarching principle of complementarity, at least in the sense that a prior and independent assessment can now be made by a state. In the fullness of time, it may actually be possible that domestic prosecutions will be undertaken for the crime of aggression. See Van Schaack, Beth, Par in Parem Imperium Non Habet: Complementarity and the Crime of Aggression , 10 J. Int’l Crim. Just. 133, 155–61 (2012)CrossRefGoogle Scholar.

⁹⁰ This language is drawn from Understanding 5.

⁹¹ Rome Statute, supra note 2, Arts. 121(1)–(3), 123(2).