Justiciability, Complementarity and Immunity: Reflections on the crime of aggression

Some 70 years after the first and, so far the only, criminal prosecutions pertaining to the ‘supreme international crime’1 took place,2 the activation of the – long dormant – jurisdiction of the International Criminal Court (ICC) over the crime of aggression appears imminent. At the time of writing, 32 States Parties had ratified the Kampala Amendments on the Crime of Aggression,3 thus exceeding the 30 ratifications required for the Court to exercise jurisdiction pursuant to Articles 15bis(2) and 15ter(2) of the ICC Rome Statute (RS).4 The moment of truth will arrive somewhere after 1 January 2017, when the Assembly of States Parties will need to adopt a decision (by consensus or at least by a two-thirds majority) affirming the Court’s jurisdiction.5 As the activation of Articles 8bis, 15bis and 15ter RS is drawing ever nearer, the debate over the prosecution of the crime of aggression – which had never really disappeared – has again taken off with renewed vigour. Illustrative in this regard is an article by Harold Koh and Todd Buchwald – respectively former Legal Adviser and former Assistant Legal Adviser to the US Department of State – in the 2015(3) issue of the American Journal of International Law in which the authors identify several shortcomings and uncertainties in the Kampala Amendments, which they urge should be addressed ahead of the activation of the Court’s jurisdiction.6 The

Utrecht Law Review | Volume 13 | Issue 1, 2017 20 the territorial State (the 'victim' -so to speak), but also by the UN Security Council. The Council can indeed sanction a variety of military interventions, whether of a humanitarian or 'pro-democratic' nature (including interventions leading to regime change) -although it arguably cannot sanction territorial annexation or purely punitive forcible actions. Clearly, this is fundamentally different for atrocity crimes, the commission of which can under no circumstances be 'authorized' by the UN Security Council (or State authorities). Accordingly, and perhaps sub-consciously, the rules governing the use of force are to a certain extent perceived not to be of the same 'fundamentally norm-creating' 11 character as, say, the rules prohibiting genocide or torture. After all, the argument goes, should we truly regard a political leader as being guilty of the crime of aggression, 'merely' because a single permanent member prevented a military intervention from being authorized by the Security Council (whereas a different vote would have meant there would not have been any wrongful conduct on the part of the intervening State to begin with)? 12 Added to this is the perverse tendency on the part of those on the sidelines to surgically detach the political decision-making process leading up to the launch of a military intervention from the destruction, loss of life (among civilians AND combatants) and other mayhem (e.g. political chaos, economic breakdown, …) that frequently follows -a tendency that is all the stronger where certain consequences are further removed in time from the beginning of the intervention and/or the causal link with the intervention is less firmly established. This is also reflected in the dominant normative account which views the crime of aggression as a wrong against a foreign State, a political crime, which plays exclusively at the 'macro' level 13 and which 'yields an abstract harm', 14 rather than as a compound of wrongs against individuals (civilians and combatants), that entails 'the slaughter of human life, the infliction of human suffering, and the erosion of human security.' 15 In the end, the sobering conclusion is that various scholars continue to believe that aggression should not be regarded as an international crime at all, let alone as the 'supreme international crime differing only from other war crimes in that it contains within itself the accumulated evil of the whole.' 16 These persistent sentiments call for some observations in relation to issues of justiciability, complementarity and immunity.

Persistent opposition to the crime of aggression's justiciability
Inasmuch as they were adopted by consensus at the plenary meeting of the (then 111-Member) ICC Assembly of States Parties, one might have expected the Kampala Amendments to be the final word on the inherent justiciability of aggression as a crime under international law, and to put to rest critiques that the ICC is fundamentally incompetent to prosecute crimes of aggression. Clearly, this has not been the case. Koh and Buchwald, for example, recently reiterated the view that '[a]ggression determinations are fundamentally different in kind [from determinations of atrocity crimes]: they fundamentally require a political assessment and political management.' 17 And, in the words of Rostow, '[d]eterminations of aggression are political and rightly so.' 18 Comments such as these are reminiscent of the Nicaragua case, where the United States went to great lengths to demonstrate that the Court was unfit to assess the legality of the US intervention in Nicaragua.
Utrecht Law Review | Volume 13 | Issue 1, 2017 Despite having itself brought cases involving the use of force before the ICJ in the 1950s, 19 the US indeed claimed at the time of the proceedings that the case involved an inherently political problem that was not appropriate for a judicial solution. According to the State Department: 'The [ICJ] was never intended to resolve issues of collective security and self-defence and is patently unsuited for such a role.' 20 As is well known, the Court rejected these objections 21 and proceeded to a ruling on the merits. Since then, the Court has in several cases 22 pronounced directly or indirectly on the compatibility of State conduct with the rules governing the use of force -as have a number of arbitral tribunals. 23 What is more, while respondent States have continued to raise various challenges to admissibility in these cases, e.g. pertaining to the indispensable parties requirement (on which, see also infra) or the difficulties concerning the collection of evidence, the allegedly 'political' nature of the dispute has no longer been raised in contentious cases before the ICJ. 24 It is firmly established then -and rightly so -that the legality of a State's recourse to (armed) force is not automatically removed from judicial scrutiny, but can be judged by an international court or tribunal (provided, of course, that its jurisdiction has been duly consented to). It is somewhat puzzling then why, if States can be found to incur international responsibility for breaching the prohibition on the use of force (and, arguably, for committing 'acts of aggression'), some still find it opportune to contest that it is possible for an international court to pronounce on an individual's criminal responsibility for the crime of aggression. This is all the more so inasmuch as the post-War precedent of criminal prosecution of individual 'aggressors' long predates the first finding of State responsibility for a breach of the prohibition on the use of force. 25 At a press briefing following the Kampala conference, the then US Legal Adviser Harold Koh actually took pride in the fact that 'as the country of Nuremberg prosecutor Justice Jackson, we are the only country that has successfully prosecuted the crime of aggression'. 26 The United States did not seem to think back in 1945-1946 that aggression was inherently political and non-justiciable. 27 Rather, the United States supported the prosecution of Nazi leaders for crimes against the peace in spite of serious concerns at the time as to the compatibility of these prosecutions with the nullum crimen sine lege principle. 28 Again, it is puzzling then to see how some continue to explicitly or implicitly question the justiciability of the crime 19 A point which the Court could not resist from highlighting in the Nicaragua case: 'It is relevant also to observe that while the United States is arguing today that because of the alleged ongoing armed conflict between the two States the matter could not be brought to the of aggression when the international criminal nature of (wars of) aggression has in the meantime been affirmed in a variety of international instruments 29 (remedying earlier concerns pertaining to the nullum crimen principle) and considering that the UK House of Lords, for instance, in 2006, confirmed that 'the core elements of the crime of aggression [are] understood (…) with sufficient clarity to permit the lawful trial (…) of those accused of this most serious crime.' 30 In the end, the large majority of legal doctrine agrees that the crime of aggression is an international crime with individual responsibility. 31 Some scholars do not go as far as to argue that the crime of aggression is inherently non-justiciable -which presupposes a disavowal inter alia of the Nuremberg precedent -, but instead present what one could call 'light' versions of the justiciability critique. Thus, it is argued that only the Security Council can determine the existence of a State 'act of aggression', which is a prerequisite for finding a crime of aggression. A variant holds that the ICC is incompetent to judge sovereign States. Others insist that the ICC is prohibited from examining the legality of the conduct of non-consenting States. Still others draw the policy card and claim that the political risk is too great for the International Criminal Court to meddle with 'questions of ultimate power' (to paraphrase Dean Acheson). 32 Each of these reservations merits brief consideration.
A first 'light' version of the justiciability critique holds that prosecution over the crime of aggression should be possible only after a prior determination by the Security Council that a State 'act of aggression' has been committed. The underlying argument again is that such prosecution presupposes a proper finding of a State 'act of aggression', a competence which 'the Charter has traditionally assigned to the Security Council' 33 -put differently, a competence which the founding fathers of the UN allegedly intended to reserve to the UN Security Council. 34 In a nutshell, leaving aside the fact that Security Council resolutions referring to '(acts of) aggression' remain rare and that no such resolution has been adopted since 1990, 35 such interpretation ascribes to Article 39 UN Charter a meaning which the founding fathers of the UN never intended. Article 39 UN Charter is an institutional provision, which determines the situations in which the Security Council may decide to take enforcement action. Such enforcement action is not limited to situations where there has been a prior breach of international law. A 'threat to the peace', for instance, does not necessarily presuppose the occurrence of internationally wrongful conduct (States do not incur international responsibility for committing 'threats to the peace' …). In a similar vein, the determination of an 'act of aggression' by the Security Council has always been regarded as a fundamentally political, 29  Utrecht Law Review | Volume 13 | Issue 1, 2017 rather than a judicial, finding, 36 let alone that the absence of such a determination should a priori preclude an actual judicial organ from inquiring into the legality of a State's recourse to force. This has been amply affirmed in the case law of the ICJ (it may be noted that, even at the time of the post-War prosecutions, no one seemed to think that prosecutions pertaining to crimes against the peace presupposed some form of formal approval by the newly-established UN Security Council). As mentioned before, the ICJ has on several occasions examined the compatibility of State conduct with the Charter and/or customary rules on the use of force. 37 More generally, the ICJ has repeatedly asserted that, in accordance with Article 24 UN Charter, the Security Council's competence in relation to the maintenance of international peace and security is not 'exclusive'. 38 This non-exclusive character is also borne out by the fact that the UN General Assembly has on numerous occasions pronounced on the legality of inter-State uses of force. 39 It follows that the pre-Kampala debate as to whether a Security Council determination that an act of aggression has been committed should be a precondition for the ICC to exercise jurisdiction is better regarded as a policy debate. 40 In the margin, there is, moreover, something fundamentally paradoxical in the position of some, such as Koh, who, one the one hand, reject a formalist reading of the UN Charter, based on a 'statist' understanding of State sovereignty that would preclude humanitarian interventions by individual States absent authorization from the UN Security Council, while nonetheless hiding behind the primacy of the UN Security Council when it comes to the justiciability of the crime of aggression.
A second version holds that the determination of an 'act of aggression' should belong to the Security Council, not because it is inherently political, but rather because, as Pellet, for instance, emphasizes, 'it is not the ICC's function to judge sovereign States'. 41 Article 1 RS effectively makes clear that the ICC has 'the power to exercise its jurisdiction over persons for the most serious crimes of international concern'. No reference is made to possible jurisdiction vis-à-vis States. Article 25(4) RS moreover adds that 'no provision in this Statute relating to individual criminal responsibility shall affect the responsibility of States under international law'.
At the same time, the critique of Pellet and others is not fully convincing. Clearly, when the ICC (or an ad hoc international criminal tribunal) is called upon to examine whether a private individual, in particular a member of a non-State armed group, has committed atrocity crimes, it is not judging sovereign States. Indeed, while the conduct of the individual concerned may or may not be imputable to a State, in such scenarios the ICC (or ad hoc tribunal) need not, and arguably should not, take a position on the matter, 'since its jurisdiction is criminal and extends over persons only'. 42 Nonetheless, it is evident that whenever the ICC is determining whether a State organ (be it a low-ranking soldier or a political or military leader) has committed genocide, war crimes or crimes against humanity, even if it is not explicitly pronouncing on the matter, it is indirectly/de facto making a finding of State responsibility as well -for the simple reason that the conduct of State organs is in principle imputable to the State, even if it is ultra vires. 43 It may moreover Note: the distinction between 'threats to the peace', 'breaches of the peace' and 'acts of aggression' was inspired in part by a desire to distinguish between situations where the Security Council would be 'obliged to act', and those where the Council would be free to choose whether or not to take action. In the end, however, the drafters of the Charter chose to grant the Security Council the greatest possible freedom in deciding on the existence of either of these thresholds and on deciding whether or not to take action. Suggestions to define the concept of an 'act of aggression' were dismissed. be observed in this context that, like aggression, genocide and crimes against humanity are by nature crimes that presuppose the collective involvement of a multitude of individuals, including the involvement of persons in a leadership position. 44 Pellet recognizes as much, by admitting that the ICC may well be called upon to judge an individual accused of genocide whose conduct is imputable to the State. Yet, he insists that there is a significant difference, in that 'the Charter expressly confers on the Security Council the responsibility to determine the existence of an act of aggression, whereas it does nothing of the kind concerning genocide.' 45 Thus, Pellet eventually falls back on the previous argument, according to which the Charter grants the Security Council allegedly exclusive competence to determine an 'act of aggression' (since 'acts of aggression' are explicitly mentioned in Article 39 UN Charter, whereas 'genocide' and 'crimes against humanity' -even if they may well qualify as 'threats to the peace' -are not). As mentioned above, this argument fails to convince. Some object that, even if ICC rulings pertaining to crimes permitted by State officials also amount to a de facto finding of State responsibility, a fundamental difference remains in that, in order to find a crime of aggression, the ICC must follow a two-tier approach, and must first make an explicit finding that a State has committed an act of aggression. 46 No such explicit finding of State responsibility is required in respect of the atrocity crimes -rather, it may at most be implicit. While this difference cannot be ignored, its impact should arguably not be exaggerated either. First, it is worth stressing that this two-tier approach was not the inevitable result of the inherent features of 'aggression', but was the result of the choices made throughout the drafting process of the Kampala Resolution. 47 Thus, instead of separating out the State act of aggression, on the one hand, and the individual involvement therein of a person in a leadership position, on the other, it would equally have been possible to merge the two steps into one, so that the determination of a State act of aggression would be implicit, rather than explicit. By way of illustration, such is the approach adopted in the definition of 'crimes against peace' in the Charter of the Nuremberg Tribunal. 48 In a similar vein, several national codes criminalize, for instance, 'planning or preparing an aggressive war', without demanding a prior and separate finding of State responsibility for an 'act of aggression'. 49 One may regret that the drafters did not opt for such a 'one-step' approach, which would have been more consistent with the other crimes within the ICC's jurisdiction. Second, as a matter of principle, States are of course free to create international courts and tribunals upon which they confer, by way of delegation, 50 jurisdiction vis-à-vis States and/or individuals. Accordingly, even if the ICC was established first and foremost to establish individual criminal responsibility for international crimes, it is difficult to understand why the ICC should be prevented from pronouncing on a State's responsibility for an act of aggression -in a manner which does not create legal consequences in terms of State liability 51  the 'Monetary Gold' principle, according to which an international court must abstain from deciding a case where the rights and obligations of a non-consenting third State form 'the very subject-matter' of the case. 53 A few cursory observations are in order. First, even if we were to assume that the Monetary Gold principle applies when the ICC is exercising jurisdiction over the crime of aggression on the basis of Article 15bis RS (State referral or proprio motu), 54 it must be recalled that the Rome Statute and the Kampala Amendments contain a range of mechanisms that restrict the Court's jurisdiction in respect of non-consenting aggressor States. 55 The cumulative impact of these provisions is that the ICC is prevented from exercising jurisdiction on the basis of State referral or proprio motu where the aggressor State is not a party to the Rome Statute, or when it is a State Party that has lodged an opt-out declaration pursuant to Article 15bis(4) RS. 56 Second, if the relevant provisions are interpreted as permitting the ICC to exercise jurisdiction pursuant to Article 15bis RS when the aggressor State has not ratified the Kampala Amendments nor lodged an opt-out declaration (specifically, where the victim State has ratified the amendments), 57 is the Monetary Gold principle infringed? Akande, for one, takes the view that, in light of Article 121(5) RS, such (aggressor) State must indeed be regarded as a 'non-consenting State', and answers in the affirmative. 58 Against this view, it may be questioned whether a State Party to the Rome Statute, which has deliberately refrained from lodging an opt-out declaration can be regarded as 'non-consenting' for present purposes (even if it has not ratified the Kampala Amendments), and/or whether such a State's rights and obligations form 'the very subject-matter' of the case before the ICC. A parallel can arguably be drawn with the advisory jurisprudence of the ICJ. On the one hand, the ICJ has stated that 'the lack of consent of an interested State may render the giving of an advisory opinion incompatible with the Court's judicial character', in particular when this would have 'the effect of circumventing the principle that a state is not obliged to allow its disputes to be submitted to judicial settlement without its consent'. 59 On the other hand, the ICJ has never refused to render an advisory opinion due to a lack of consent, even in cases (such as the Palestinian Wall case 60 ), where the Court undeniably pronounced on the rights and obligations of individual States. 61 In the ICJ's Peace Treaties Opinion, this approach was ostensibly justified by reference to the 'advisory' character of the Court's opinions and the fact that they have 'as such, (...) no binding force'. 62 It must be conceded that the PCIJ has on one occasion refused to render an advisory opinion due to a lack of consent, notably in the Eastern Carelia case, which involved an ongoing dispute between Finland and the Soviet Union. Yet, this different approach in the Eastern Carelia case can be explained by the fact that the PCIJ was asked to pronounce on the rights and obligations of the Soviet Union, which was not a Member of the League of Nations to begin with. 63 For present purposes then, it could be argued that whenever the ICC exercises jurisdiction under Article 15bis RS in connection with an aggressor State that is a State Party to the Rome Statute, but which has not ratified the Kampala Amendments nor lodged an opt-out declaration, the situation is more akin to the Peace Treaties scenario than to the Monetary Gold scenario or the Eastern Carelia scenario. The reason for this is twofold. First, the aggressor State is a State Party to the ICC Rome Statute and has agreed, as a matter of principle, to the exercise of the jurisdiction of the Court in respect of the crime of aggression pursuant to Article 5(2) Rome Statute. Second, as is also confirmed by Article 25(4) RS, a finding of an 'act of aggression' by the ICC has -to paraphrase the Peace Treaties Opinion -'no binding force' of its own for the aggressor State. 64 In the end, it must be emphasized that the critique relating to the 'consent problem' does not challenge the justiciability of the crime of aggression as such, nor the authority of the ICC to adjudicate the crime, but only challenges the 'scope' of the ICC's jurisdiction. Finally, it is no secret that the activation of the Court's jurisdiction over the crime of aggression may inject it in treacherous political waters, and may test its legitimacy and credibility. Koh and Buchwald illustrate this by reference to the hypothetical scenario of two warring States, finally ready to sign a peace treaty, yet each insisting on assurances that their leaders will not be prosecuted for having started the war. 65 The authors question whether 'claims of justice [should] obstruct peace'. 66 At the same time, it is difficult to see how this situation is fundamentally different from the conclusion of a peace agreement ending a non-international armed conflict and providing for broad amnesty for war crimes. Both scenarios raise similar questions pertaining to the permissibility and international recognition of amnesties. 67 Of course, the likelihood that the prosecution of 'aggressors' will provoke political reactions is overall greater than with the prosecution of atrocity crimes. Yet, as is the case for the other reservations discussed above, this is a difference in degree, not a difference in nature. 68 The political exposure is not exclusive to the crime of aggression. The previous record of the ad hoc tribunals and the ICC indeed suggests that the prosecution of high-ranking officials, including sitting Heads of State, for crimes against humanity, can be just as politically sensitive as the prosecution of the leader of a (State or non-State) armed group for genocide. Yet, in these cases, the justiciability of the crimes concerned is not fundamentally in dispute, and the (potential) political backlash is not generally seen as a valid reason why the international community should tolerate impunity in perpetuum. Why, then, should it be different for the crime of aggression?

Complementarity and immunity
An important reason why some have expressed concern over the Kampala Resolution and the impending activation of the ICC's jurisdiction over the crime of aggression concerns the 'spill-over' effect 69 to the national level, in particular the fact that a growing number of States may adopt domestic legislation criminalizing the crime of aggression. States may do so in order to make sure, in accordance with the complementarity principle, that political or military leaders can be tried before their own national courts, rather than face justice in The Hague. 70 If such a prosecution at the national level of one's own nationals -unlikely though it may be -does not give rise to objections, the prospect of States establishing and exercising similar criminal jurisdiction vis-à-vis nationals of third States is highly controversial. Since the adoption of the Kampala Resolution, eight countries have effectively (at the time of writing) adopted amendments to their Utrecht Law Review | Volume 13 | Issue 1, 2017 Criminal Code, incorporating the crime of aggression. 71 What is more, all of these provisions explicitly or implicitly use the Rome Statute definition as the international standard reference (albeit that there are also major differences between the various provisions). 72 Influenced by civil society campaigns, other countries may well follow suit.
It is clear that the crime of aggression does not easily fit with the ICC's complementarity concept. 73 Indeed, whereas prosecutions of political or military leaders suspected of international crimes before their own national courts have generally been the exception, rather than the rule, it is particularly naïve to expect a proliferation of prosecutions against suspected 'aggressors' before their own national courts. Thus, while several countries had domestic provisions criminalizing aggression well before the Kampala conference, the crime of aggression has remained a paper tiger ever since the last of the Nuremberg proceedings. Since 1949, there has not been a single indictment on this basis. 74 In Germany, the Federal Public Prosecutor rejected requests to commence criminal proceedings against members of the government in relation to the German participation in Operation Allied Force, as well as for granting the US and its allies in the 2003 Iraq war overflight rights and allowing them to transport troops and supplies through Germany. 75 Similarly, requests to instigate criminal proceedings against government members for involvement in the Iraq war were declared inadmissible in Spain and Belgium. 76 The Statute of the 'Iraqi Special Tribunal' did include among the bases for jurisdiction 'the threat of war or the use of the armed forces of Iraq against an Arab country, in accordance with Article 1 of [Iraqi] Law Number 7 of 1958, as amended' (Article 14(c) of the Statute) 77 (a reference to 'aggression' was carefully avoided in light of the contested legal basis of the USled intervention). Eventually, however, Saddam Hussein was hanged before a case under Article 14(c) got underway. 78 In all, the trend towards greater parliamentary involvement (at least in Western liberal States) in decisions pertaining to the deployment of armed forces abroad, 79 as well as to a growing degree of post facto political accountability, 80 has not translated into greater judicial scrutiny of government decisions relating to military The growing number of domestic criminal codes incorporating the crime of aggression are unlikely to alter this. National courts are indeed traditionally reluctant to review 'battlefield decisions', especially when they concern high-ranking officials. 82 According to Lord Hoffman, 'the making of war and peace and the disposition of the armed forces has always been regarded as a discretionary power of the Crown into the exercise of which the Courts will not enquire'. 83 The same aversion is echoed in the ruling of the US Court of Appeals in the El-Shifa Pharmaceutical Plant case: 'Courts are not a forum for second-guessing the merits of foreign policy and national security decisions textually committed to political branches'. 84 And even if the coming to power of a new government may exceptionally pave the way for national prosecutions against former political or military leaders with blood on their hands, there is a further reason why such prosecutions -in spite of the catharsis effect they might occasionally produce -are even more unlikely with regard to the crime of aggression, than with regard to atrocity crimes, or at least atrocity crimes committed in the context of a non-international armed conflict. The reason for this is that a national court finding a (former) leader guilty of aggression would ipso facto also be recognizing the country's international responsibility vis-à-vis the victim State. Such a self-incriminating effect hardly makes prosecution at the national level an attractive option (especially inasmuch as a breach of the jus ad bellum makes a State liable for all consequences that could reasonably be foreseen at the outset, 85 and may thus result in a liability that is exponentially larger than with regard to grave breaches of the law of armed conflict that are imputable to the State). It follows from the foregoing that, contrary to what is the case for the atrocity crimes, the complementarity principle is not perceived as an escape route, or a safety valve, to avoid proceedings against one's nationals before the ICC in respect of the crime of aggression. This is one of the factors explaining why States chose to introduce various restrictions to prevent the Court from prosecuting leaders from non-consenting States for the crime of aggression (save in the scenario of a Security Council referral). 86 These 'consent-based' mechanisms do not come into play, of course, with regard to domestic proceedings against nationals of third States who are suspected of having committed the crime of aggression. Although no such precedents have yet occurred since the late 1940s, 87 several scholars have expressed concerns over the growing number of criminal codes criminalizing aggression and, concomitantly, the increased likelihood of proceedings against alleged aggressors before the national courts of victim States and other third States. 88 Such proceedings are perceived to contravene the fundamental principle of sovereign equality and are feared to engender serious implications for international relations and international peace and security. 89 Utrecht Law Review | Volume 13 | Issue 1, 2017 This was also the position of the ILC in its 1996 draft Code of Crimes against the Peace and Security of Mankind. 90 Given the risk of 'serious implications for international relations and international peace and security', the ILC indeed took the view that jurisdiction over the crime of aggression ought to rest exclusively with an international criminal court, with the exclusion of national courts -save for the national courts of the State whose leaders allegedly participated in the act of aggression. 91 In the wake of the Kampala Review Conference, several proposals have been made, including some ranging from the unproductive to the absurd, to take measures prior to the activation of the ICC's jurisdiction in order to eliminate or mitigate the risks of domestic prosecution before the courts of third States (including one proposal which would have the ICC Chief Prosecutor issue an official statement 'discouraging domestic incorporation' of the crime of aggression). 92 Others, however, have instead expressed sympathy for the victim's interest in holding third-State leaders responsible for crimes of aggression. 93 In the present author's view, the prospect of criminal proceedings in Tehran against Israeli leaders with regard to military operations in Gaza or in southern Lebanon is hardly appealing, as is, for that matter, the prospect of criminal proceedings in Kiev, conducted in absentia, against Russian leaders pertaining to the annexation of Crimea. For present purposes, however, we will limit ourselves to some cursory observations.
It is correct that the prosecution of non-nationals for the crime of aggression before domestic courts is at first sight difficult to reconcile with the principle of sovereign equality and the par in parem axiom 94 -as was also acknowledged by the ILC in the Commentary to the 1996 draft Code of Crimes against the Peace and Security of Mankind. 95 First, inasmuch as a crime of aggression presupposes a State act of aggression, such proceedings indeed imply that the domestic courts of one country sit in judgment upon the State acts of other countries. 96 Such conduct would appear to be at odds with State immunity from jurisdiction, which also -as the ICJ confirmed -extends to grave breaches of international law and to breaches of peremptory norms. 97 Second and related, the prosecution of individual 'aggressors' would also seem to be at odds with the (derived) immunity ratione materiae of State officials.
As far as the latter immunity is concerned, it is clear that, inasmuch as the crime of aggression is a 'crime of leaders', which can be committed only by 'a person in a position effectively to exercise control over or to direct the political or military action of a State', it must undoubtedly be regarded as 'an act performed in an official capacity'. 98 Yet, the same also appears to be true in respect of several other international crimes. As ILC Special Rapporteur Escobar Hernández observed in her Fourth Report on the immunity of State officials from foreign criminal jurisdiction, 'the argument that torture, enforced disappearances, extrajudicial killings, ethnic cleansing, genocide, crimes against humanity and war crimes are devoid of any official or functional that it remains to be seen if the trend will change 'now that a consensus definition of the crime has emerged'). Van Schaack, supra note 70, pp. 144-145. At the same time, it is observed that various national criminal codes effectively foresee the application of forms of extraterritorial jurisdiction 'that clearly are or could be understood as forms of universal jurisdiction to the crime of aggression' (Coracini, supra note 71, pp. 1068-1069). Arguing that 'the Nuremberg trial and its progeny crystallized the right under customary international law of states to exercise universal jurisdiction' over the crime of aggression, see: Scharf, supra note 68. In a similar vein, Wrange, supra note 31, pp. 718-720. 90 ILC, 'Draft Code of Crimes against the Peace and Security of Mankind -with commentaries', Yearbook of the International Law Commission (1996), Vol. II, Art. 8, Commentary para. 14. 91 Ibid., Art. 8, see also paras. 14-15 of the Commentary to Art. 8. According to the ILC, the prosecution of an individual for the crime of aggression by the national courts of the State concerned could be 'essential to a process of national reconciliation'. Moreover, such prosecution 'would not have the same negative consequences for international relations or international peace and security', as national courts of such a State could determine the responsibility of a leader for the crime of aggression 'without being required to also consider the question of aggression by another State'. 92 See Veroff, supra note 88, pp. 764-765. Veroff proposes four possible interventions: 'The States parties should (1) establish exclusive ICC jurisdiction or primacy over the crime of aggression; (2) urge the ICC's Chief Prosecutor to issue an official statement discouraging domestic incorporation; (3) encourage domestic prosecutions for ordinary crimes instead of aggression; and (4) generate a multifactor list to guide domestic prosecutions to avoid the most problematic prosecutions and mitigate the associated harms.' 93 E.g. Pellet, supra note 8, p. 564. According to Clark, 'many members of the SWGCA were comfortable with victim state (…) jurisdiction'.
Clark, supra note 2, p. 795. 94 As well as, in those common-law countries practising it, with the act-of-State doctrine. 95  dimension in relation to the State is at odds with the facts'. 99 As noted above, whenever national courts pronounce on the individual criminal responsibility of an official (or former official) from a third State for, say, war crimes, they are de facto taking a stance on the responsibility of the latter State (since the conduct of the official is in principle imputable to that State, even if conducted ultra vires). It follows that such a prosecution creates the same tension with the par in parem principle which the prosecution of the crime of aggression before the national courts of third States ostensibly gives rise to. What is more, under the UN Convention against Torture (CAT) and the UN Convention on Enforced Disappearances (CED), the official character is a constitutive element of the prohibited acts which States are required to criminalize and prosecute. 100 In spite of this, there is undoubtedly a degree of support in legal doctrine, as well as in State practice, for the view that (former) high-ranking officials -other than those endowed with absolute personal immunity during their time in office -cannot hide behind their material immunity from jurisdiction to escape prosecution for various international crimes, such as torture and genocide. 101 By way of illustration, 'Draft Article 7', put forward by ILC Special Rapporteur Escobar Hernández in her Fifth Report on the immunity of State officials from foreign criminal jurisdiction expressly states that immunity shall not apply in respect of '[g]enocide, crimes against humanity, war crimes, torture and enforced disappearances'. 102 Of course, the assumption here is also that the prosecution of foreign officials for certain international crimes is not incompatible with State immunity from jurisdiction either. In other words, the (unspoken) assumption is that even if the conviction of a foreign official by a national court for an international crime entails a de facto finding of State responsibility, such a finding does not of itself give rise to a breach of State immunity. Why, then, would this be different in respect of the crime of aggression? As mentioned before, it has been argued in this context that the crime of aggression is different -even from those crimes, such as enforced disappearances under the CED, where the official character is an indispensable elementbecause the national court would be pronouncing explicitly/directly, instead of implicitly/indirectly, on the responsibility of a third State. Whether such an intermediary finding, which does not have direct legal consequences for the third State, qualifies as an exercise of jurisdiction vis-à-vis the latter State, in breach of its immunity from jurisdiction, is open to debate. 103 If the answer would be positive, a breach of State immunity could arguably be avoided by abandoning the two-tier approach put forward in Article 8bis RS, and instead adopting national legislation defining the crime of aggression in a manner that 'merges' the 99 See ibid., paras. 121-126. See also ibid., paras. 61-77 (referring inter alia to the fact that, under the 1984 Convention against Torture, 'the official status of the act is an undeniable component of torture'). While a divergent view holds that the perpetration of a crime under international law cannot be qualified as an official act, but must be treated as a private act for which no immunity is accorded, Kreicker observes that: 'this artificial attempt to set aside state immunity, which has rightly been rejected by the ICJ and by a clear majority in literature, ignores the obvious fact that crimes under international law are typically committed in the exercise of military and police power -that is, sovereign power.' See: H. Kreicker, 'Immunities', in Kreβ & Barriga, supra note 31, pp. 675-703, at 680 (with further references in respect of both opposite views). In a similar vein: Scharf, supra, note 68, pp. 383-384. 100 Pro memorie: the Convention against Torture (CAT) defines 'torture' as 'any act by which severe pain or suffering (...), is intentionally inflicted on a person for such purposes as obtaining from him or a third person information or a confession, punishing him for an act he or a third person has committed or is suspected of having committed, or intimidating or coercing him or a third person, or for any reason based on discrimination of any kind, when such pain or suffering is inflicted by or at the instigation of or with the consent or acquiescence of a public official or other person acting in an official capacity.' (emphasis added) (Art. 1(1)). Art. 2 of the Convention on Enforced Disappearances (CED) defines enforced disappearance as 'the arrest, detention, abduction or any other form of deprivation of liberty by agents of the State or by persons or groups of persons acting with the authorization, support or acquiescence of the State, followed by a refusal to acknowledge the deprivation of liberty or by concealment of the fate or whereabouts of the disappeared person, which place such a person outside the protection of the law.' (emphasis added). Both Conventions require States Parties to exercise jurisdiction on the basis of the territoriality principle, the active personality principle and permit the exercise of jurisdiction on the basis of the passive personality principle. In addition, in respect of alleged offenders present on the State's territory, both Conventions establish an 'aut dedere, aut judicare' duty. Art. 5 CAT, Art. 9 CED. 101 Further: see R. Pedretti, Immunity of heads of State and State officials for international crimes (2014). Note that this argument is not limited to international crimes for which there is an explicit treaty obligation to exercise some form of criminal jurisdiction (in particular torture and enforced disappearances), but is also made in respect of crimes where no such treaty exists (as yet) (e.g., crimes against humanity). See also: Kreicker, supra note 99, p. 681 ('State practice supports a customary international law exception to the general functional immunity in cases of crimes under international law, as is evidenced by many court decisions. A clear majority in scholarly writing also supports the existence of such an immunity exception.').  104 This is, for instance, the approach adopted in Article 13 of the Arab Draft Model Law for the Crimes falling within the jurisdiction of the ICC, as well as in several older national laws criminalizing aggression/aggressive war. 105 It is admitted, however, that recent national legislation often adopts the two-step approach of Article 8bis RS. On a different note, while an in-depth assessment of immunity law is beyond the scope of the present paper, it is worth observing that States are not necessarily consistent in their approach with respect to the jurisdictional immunity of States and foreign officials, and their deference to the par in parem axiom. 106 By way of illustration, while the US position would seem to be that it enjoys jurisdictional immunity before foreign courts with regard to a US drone strike killing a taxi driver in Pakistan, with regard to weapons supplies to Syrian rebel groups, or with regard to its military interventions in Syria and elsewhere, its Foreign Sovereign Immunities Act (FSIA) contains an exception in respect of countries which the US Department of State has unilaterally decided to qualify as 'state sponsors of terrorism'. 107 The so-called 'terrorism exception' to the FSIA would permit litigation against the Syrian regime for providing funds to Hezbollah, and has, for instance, been used to seize USD 2 billion in Iranian assets inter alia because of Iranian funding and assistance to Islamic Jihad in Gaza. 108 The main message here is again that the 'crime of aggression' is not fundamentally or intrinsically different from various other international crimes, which (when committed by (former) State organs) may equally qualify as 'acts performed in an official capacity', 109 but which part of this legal doctrine can be prosecuted without giving rise to insurmountable obstacles from an immunities perspective.
In the end, even if the complementarity principle may constitute an incentive for domestic legislation, 110 the peripheral problem pertaining to the possibility and prospect of domestic prosecution against nonnationals over the crime of aggression transcends the treaty context of the ICC Rome Statute and the activation of the ICC's jurisdiction with respect to this crime. It is a general international law problem that merits greater attention in particular in the context of the International Law Commission's ongoing work on the immunity of State officials.
As mentioned above, in her Fifth Report on the immunity of State officials from foreign criminal jurisdiction of June 2016, ILC Special Rapporteur Escobar Hernández takes the view that material immunity does not apply in respect of '[g]enocide, crimes against humanity, war crimes, torture and enforced disappearances'. 111 Interestingly, 'the crime of aggression' is not included in the list, thus signalling that, in the Special Rapporteur's view, a customary international law exception to immunity has not yet emerged in respect of this crime. 112 The Special Rapporteur cites several reasons to account for this: 113 'the Court's jurisdiction over this crime is optional and not automatic, as is the case with the other international crimes; the Commission itself already indicated in the draft Code of Crimes against the Peace and Security of Mankind of 1996 that the crime of aggression must be entrusted primarily to international courts and tribunals, given the political implications it could have for the stability of relations between States; there are very few pieces of national criminal legislation that address this crime; and, lastly, there do not appear to be any cases of State practice in which the crime of aggression has been characterized as a limitation or an exception to the exercise of immunity, at either the legislative or the judicial level.' The reasoning of the Rapporteur is only partially convincing. 114 It seems to ignore that there have been at least a few examples of victim State jurisdiction over the crime of aggression, 115 and that the number of criminal codes incorporating the crime of aggression is on the rise (and that these criminal codes constitute State practice suggesting that material immunity does not necessarily apply to the crime of aggression).
Whether or not the crime of aggression is eventually included in the list of acts for which the immunity shield is pierced may well have a significant impact on the debate in legal doctrine, and on future State practice. At the time of writing, there appeared to be little appetite among the ILC members for removing immunity for crimes of aggression. 116 It also remains to be seen how a future ILC Draft will be received in the Sixth Committee of the UN General Assembly. Whatever the outcome, it is submitted that the controversy concerning the possible prosecution of the crime of aggression at the national level should not be allowed to weigh in on, let alone derail, the final activation of the ICC's jurisdiction. Pro memorie, several countries criminalized aggression at the domestic level long before the adoption of the Rome Statute. Furthermore, as 'Understanding 5' adopted by the Assembly of States Parties in 2010 (pursuant to a US proposal) stresses, the Kampala Amendments should 'not be interpreted as creating the right or obligation to exercise domestic jurisdiction with respect to an act of aggression committed by another State'. 117 This is all that needs to be said on the matter in the ICC context.

Concluding thoughts
At least symbolically, the full activation of the ICC jurisdiction over the crime of aggression will be a defining moment in the development of the international legal order, completing a process that was started in Versailles at the end of the First World War and which reached its point of no return at the 2010 Kampala Review Conference. It is surprising to see then how lukewarm (or downright critical) many (if not most) international lawyers are about the prospect of the ICC prosecuting alleged 'aggressors'. The reasons for this lukewarm reception are manifold of course. They include inter alia concerns about the definitional uncertainties left open by the Kampala definition of aggression, scepticism about the competence and authority of the ICC judges to interpret and apply the international legal framework governing the use of force, concerns over the collection of evidence, 118 etc. Many scholars also see the ICC's jurisdiction over the crime of aggression as a Trojan horse, fearing that the exercise of such jurisdiction will erode the legitimacy of, and political support for, the Court (a prospect that is particularly dire at a time when the ICC is suffering an unprecedented crisis of legitimacy inter alia in the wake of the South African withdrawal from the Rome Statute in October 2016). The latter position brings to mind the concern expressed in the wake of the ICJ's Nicaragua case -which led the United States to revoke its declaration accepting compulsory jurisdictionthat the Court's entry into the realm of 'high politics' would harm its prestige and negatively impact its caseload. 119 In reality, however, it seems that the opposite has proved true. 120 Criticism of pro-Western bias on behalf of the ICJ has faded and several countries have brought cases before the Court which either directly involved the use of force or which dealt with boundary disputes in situations of armed conflict. 121 Whether the same will be true for the International Criminal Court only time can tell.
The present essay does not pretend to provide an answer to all (or even most) of the concerns pertaining to the impending activation of the ICC's jurisdiction over the crime of aggression. Instead, we have essentially limited ourselves to two points. First, we have taken aim at the lingering argument that the crime of aggression is inherently non-justiciable, as well as at 'light' versions of this justiciability critique (which hold, for instance, that only the Security Council can determine the existence of (an act of) aggression, or that the ICC should refrain from judging sovereign States -even if only indirectly). Second, we have taken a closer look at claims that the activation of the ICC's jurisdiction over the crime of aggression simultaneously creates an incentive for the prosecution of alleged aggressors at the national level (and for the introduction of domestic legislation paving the way for such prosecutions) in a manner which is incompatible with the international immunities of States and foreign officials. Here, we argued that the possibility of such domestic prosecutions transcends the treaty context of the ICC Rome Statute. It is a general international law problem that merits greater attention in particular in the context of the ILC's ongoing work on the immunity of State officials. It should not, however, be allowed to derail the final activation of the ICC's jurisdiction.
The activation of the jurisdiction over the crime of aggression is bound to present the ICC and, specifically the ICC Prosecutor, with daunting challenges. Perhaps the most fundamental obstacle consists of the lingering taboo that envelopes the notion of the 'crime of aggression'. This taboo is evident from the dominant, but flawed, perception that aggression is no more than a wrong against a foreign State, a political crime, which plays exclusively at the 'macro' level 122 and which 'yields an abstract harm', 123 and which should therefore not be placed on an equal footing with the atrocity crimes, rather than as a compound of wrongs against individuals (civilians and combatants alike) that entails 'the slaughter of human life, the infliction of human suffering, and the erosion of human security'. 124 It is only by picking up the Nuremberg legacy and implementing Article 8bis Rome Statute that the International Criminal Court will bring about a much needed changement d'esprit in this regard.