In an article at Just Security last week, Michael Adams expressed surprise at the lack of attention on these and other pages to the possibility that the U.S. Tomahawk strikes on the al-Shayrat airbase in Syria were not just illegal, but also criminal. The possibility was raised by Vladimir Putin’s condemnation of the attack as an “act of aggression.”

The obvious response to this surprise might be that, whatever its normative significance, the criminality vel non of the strikes is, in practice, an irrelevance from the American perspective. The United States is arguably not subject to the jurisdiction of the International Criminal Court (ICC), much less to its narrower jurisdiction over aggression, which is anyway still pending and inapplicable to attacks on non-ICC-parties like Syria. Moreover, although aggression’s customary criminality is recognized by the DoD (para. of the Department’s Law of War Manual), aggression is not a domestic crime in the United States, which has anyway made clear that it does not consider the Kampala amendments to reflect the contours of the customary crime.

However, this response is too simplistic. Even from a purely pragmatic perspective, decision-makers in Washington would do well to pay attention to the issue of criminality when the US uses force, at least once aggression is activated at the ICC (likely at the end of this year). If a possible, proposed, or ongoing American use of force would meet (even potentially) the criteria for a criminal aggression, this would:

  • deter foreign cooperation with the action, including among longstanding US allies;
  • raise the costs to the United States of any Security Council referral of the relevant situation to the ICC, thus all but eliminating the prospect of such referral;
  • open the door to judicial rulings on the action, with significant implications both for the United States’ global reputation and for the development of the jus ad bellum (the law governing when states can use military force); and
  • more speculatively, provide the basis for the refugee claim of any US soldier (or allied soldier) facing domestic punishment for refusing to participate in the war (an avenue that once, again, opens US policy to legal challenge before foreign courts).

In what follows, I leave aside the question of whether the strikes on al-Shayrat were in fact criminal. The sole object of focus here is why the answers to questions of that kind matter in Washington. The al-Shayrat strikes may not be the last occasion, especially over the next four years, for us to reflect on these questions.

1. Foreign cooperation

Perhaps the most obvious impact of criminality on the United States would be on the prospect of obtaining and maintaining foreign cooperation. Pursuant to article 121 and to the pending article 15bis of the Rome Statute, once the amendments are effective, the ICC will have jurisdiction over all cases in which:

  • participants on both sides are ICC States Parties;
  • either the alleged aggressor state or the alleged victim state has ratified the Kampala amendments, (although there is room for interpretive debate on whether both must have ratified the amendments); and
  • the alleged aggressor state has not opted out of ICC aggression jurisdiction.

Key US allies are potentially subject to the ICC’s aggression jurisdiction on this basis. Half of NATO states, including Germany (with its US military bases), Poland (a significant contributor to the 2003 invasion of Iraq), and Belgium (the seat of NATO decision-making) have ratified the Kampala amendments. Other leading NATO and non-NATO allies like the UK, Australia, France, and Canada are ICC States Parties. The key question, from the US perspective, is: under what conditions would such leaders be criminally liable for cooperating in a US act of aggression?

Per article 8bis, it is criminal for a person with control over a state to “plan[], preparat[e], initiat[e] or execut[e]” a manifestly illegal act of aggression. The usual Rome Statute modes of liability apply (including aiding and assistance and contributing to the commission of a crime by a group acting with a common purpose), but, again, “only to persons in a position effectively to exercise control over or to direct the political or military action of a State.” (art 25(3bis)).

Interpreting this statutory framework broadly, one might reason that the leader of an allied state that assists the US in planning or perpetrating an aggression would thereby be an accessory to the crime, even if her own state did not fight in the war. If that were correct, and assuming the appropriate mens rea, criminal liability would attach to all sorts of cooperation with a US aggression, perhaps including intelligence sharing or voting in favor of authorizing the operation in the North Atlantic Council.

However, this interpretation is not without difficulty. First, it is not clear that the jurisdictional requirements would be met if only an accessory state and the attacked state are States Parties. Second, accomplice or accessory liability probably does not extend this far in the case of aggression. The Elements of the Crime state that the accused must have been “in a position effectively to exercise control over or to direct . . . the State which committed the act of aggression.” (Element 2). Although the Elements pertain to the principal perpetrator, the explicit extension in article 25(3bis) of this so-called “leadership element” to those responsible through accomplice or accessory modes of liability was intended to ensure that it would “apply to both primary and secondary perpetrators” (p.22 of Kreß & Barriga’s Travaux).

It is likely, then, that criminal liability for aggression (direct or complicit) is limited to leaders of states that actually commit aggression. The one form of inter-state assistance that unequivocally counts as aggression is when one state “allow[s] its territory, which it has placed at the disposal of another State, to be used by that other State for perpetrating an act of aggression against a third State.” (article 8bis(2)(f) & G.A. Res 3314). Beyond that, things are less clear.

Although the issue remains disputed, a common view is that the list of acts of aggression in article 8bis(2) is open rather than exhaustive. In light of that, it is conceivable that other forms of support for another state’s aggression could count as acts of aggression in themselves and not merely as secondary assistance (the ILC’s Draft Articles are instructive on the distinction). But there is little to indicate that such would be the case. Notably, the ICJ held in Nicaragua that a state would have perpetrated an armed attack via rebels only if it “sent” rebel forces, and not if it merely provided weapons and logistical support. Equally notable, that restrictive interpretation (as distinct from its broader test for what constitutes a basic “use of force”) was itself informed by the list in the General Assembly’s definition of aggression (which is identical to that in article 8bis(2)). In other words, the ICJ articulated a limited definition of indirect forms of aggression by taking a page from the very same words used in the ICC’s text on aggression.

A good reason for the ICC itself to proceed with caution here is that if it holds that various forms of cooperation would themselves constitute aggression (rather than merely illegal assistance to the aggression of another), this would imply that the attacked state would have a right to use defensive force against the state engaged in the assistance or cooperation, and not just the primary aggressor. (On the link between “act of aggression” and the “armed attack” trigger for self-defense, see here).

In light of all of this, it would not be surprising if the ICC were to take a conservative approach to the scope of transnational accessory liability for aggression, refraining from going much further than the territorial assistance identified explicitly in 8bis(2). However, until we have greater clarity on that front, the uncertainty is likely to cause at least some allies to be restrictive in the cooperation they provide any US action that might plausibly constitute a criminal aggression. The legal risks will, of course, be clearer and greater for those allies who might place their territory at the disposal of US forces conducting the armed actions.

2. Security Council referral

Any notion of prosecuting Donald Trump or another US leader for the strikes against Syria would be precluded by an abundance of legal obstacles. However, with the exception of temporal jurisdiction, all of these could in theory be overcome in one fell swoop, if the Security Council were to refer the general situation of crimes committed in the country (see article 15ter).

It might seem preposterous to believe the United States would ever allow such a referral to go ahead. But such an outcome could arise through a lack of forethought. After all, the United States voted for referral of the Syrian situation to the ICC in 2014. It was not inconceivable when it did so that 30 states would ratify the Kampala amendments, the Assembly of States Parties would approve them, and the United States would subsequently want to launch an attack on the Syrian armed forces. In fact, precisely that situation almost occurred.

In the Darfur (para 6) and Libya (para 6) referrals the US strategy for protecting any of its troops that might become involved from war crimes jurisdiction had been to insert a paragraph in the referral shielding outside actors from criminal liability. It did so again in the draft Syria referral. However, by that time, the Office of the Prosecutor had indicated (para 54) that it does not consider such restrictions to be legally effective (presumably on the persuasive grounds that once such a situation has been referred, the rule of law demands that all international crimes in that situation are under ICC jurisdiction). Despite that, the US still voted for the Syria resolution.

If Washington maintains its faith in such exemption clauses in Security Council referrals, but the ICC rejects such clauses’ validity, it is not unfathomable legally that a US vote in the Security Council would lay the foundations for the criminal liability of US leaders for aggression in The Hague. Politically, of course, it is difficult to see a weak court adopting such a bold stance, but it cannot be ruled out.

If, given that risk, Washington ceases to predicate its fate on the exemption clauses, three implications arise.

First, if the Security Council has already referred a situation, this may deter the United States from participating in an unauthorized intervention in that situation. Second, and conversely, if the United States has already intervened militarily without clear legal basis, it is unlikely to allow any Security Council referral of the situation to the ICC, unless there is very clear guidance from the Court that such interventions are not criminal. Third, going forward, the United States may be less likely to allow Security Council referrals to the ICC in any situation in which there is even a slight possibility that it might choose to engage in a legally dubious intervention in the future.

As exemplified by the Darfur and Libya referrals, even in the absence of jus ad bellum worries, the United States is keen to shield its nationals from possible war crimes jurisdiction in such conflicts. Nonetheless, given the particularly deep opposition of the US government to the criminalization of aggression, the prospect of an American indicted on that charge is likely to provoke a significantly stronger reaction.

3. The impact of foreign judgments

Given the obstacles discussed above at the ICC, the impact of head of state and official immunities in foreign domestic courts, and the difficulty of universal jurisdiction in the context of aggression, the prosecution of a US leader in The Hague or in one of the over thirty-five states that include aggression in their domestic criminal codes is highly unlikely. However, as discussed in Section 1, in the right circumstances, a prosecution could proceed against a cooperating allied leader (whether at the ICC or at home).

Quite apart from its impact on future cooperation, such a prosecution would itself be significant in exposing US conduct – which would otherwise almost certainly escape judicial review — to vicarious legal scrutiny. On the level of state responsibility, an analogous jurisdictional avenue has produced the most searching judicial review of the post-9/11 torture and detainee abuse regime (see El-Masri, Al-Nashiri, and, prospectively, Belhaj). A key US ally’s conviction in an aggression prosecution related to a US-led operation could cause even greater embarrassment in Washington and further weaken the United States’ global standing.

Such a ruling (or indeed an acquittal) might also matter in a broader sense. In principle, the crime of aggression covers only a narrow range of the gravest and clearest illegal uses of force. However, given the dearth of court decisions on the jus ad bellum, aggression rulings may affect the broader regime on the use of force more than is strictly legally appropriate. For example, an ICC ruling that a humanitarian intervention is not criminal could accelerate the legalization of such actions, even though the non-criminality of such an action does not entail that it is lawful. (On the accumulated erosion of the law in this space, compare the recent posts of Anthea Roberts and Monica Hakimi over at EJIL:Talk!). Conversely, the conviction of a foreign leader whose state participated in a US-led humanitarian intervention could have the opposite effect. Either way, the decision would shape the legal advice given to leaders across the world, perhaps overriding efforts in Washington and elsewhere to avoid taking a position on the issue.

One last note for this line of analysis: many, if not all, of these effects may also arise out of national-level (or even UN led) commissions of inquiry and the like. In other words, these political and legal effects are not limited to the prospect of a criminal case before a judicial body. Other forums, which have a greater likelihood of materializing, may also inquire into allies’ involvement in US aggression, with similar collateral consequences for the United States.

4. Soldiers and refugees

Prosecutions aside, foreign courts could also be involved in a final way in which the criminality vel non of a US action might matter in Washington. Under both the UN Refugee Convention (art 1(F)(a)) and the EU’s 2011 Refugee Directive (art 12(2)(a)) perpetrators of criminal wars are excluded from refugee status, even if otherwise eligible. Perhaps more significantly, the UN High Commissioner for Refugees’ official guidance indicates that those who flee orders to participate in an action condemned by the international community” are eligible for refugee status (here para 171). On a leading view, international crimes, including aggression, are by definition “condemned by the international community” for these purposes. See also the EU Directive, art 9(2)(e). In forthcoming work, I argue that, given the central role of unjustified killing and human violence in the wrong of aggression, this protection ought to be extended not only to soldiers who refuse to perpetrate war crimes, but also to those who refuse to fight in aggressive wars. Whether this will take hold remains uncertain, but the breadth of analysis of the crime of aggression following the Kampala amendments may help both to inform those who might refuse to fight on this basis and to generate a renewed evaluation of the legitimacy of such refugee claims by asylum authorities receiving such troops.

The current case of Captain Nathan Smith’s demand for judicial scrutiny of the domestic lawfulness of the US action against the Islamic State has rightly been the subject of much discussion on these and other pages (here, here, and here). Were it to be successful, Smith’s case could prove to be a significant inflection point in generating judicial review and grassroots enforcement of the War Powers Resolution. The successful asylum claim of a member of the US military who refuses to participate in a criminally aggressive US action could have a similar significance for international law.

As a final note on this point: it is also possible that soldiers refusing to participate in aggressive wars could have a claim to human rights protection as conscientious objectors. Most human rights bodies have focused on pacifists’ rights in this respect, rather than tying the right to conscientious objection to the illegality (or indeed criminality) of the action. However, in 2005 the Bundesverwaltungsgericht (German Federal Administrative Court) granted protection to a conscientious objector based on a legal analysis of the use of force in question, and there have also been occasional efforts in that direction at the international level (see here paras 5, 28, 37, 46-47, 145 and here art 5(2)). Were these advanced further, particularly in a supranational court with binding authority, like the European Court of Human Rights, this could affect US allies and provide another route to foreign court rulings on US actions.

* * *

Neither Donald Trump nor any US leader that wages a criminal war in the foreseeable future is likely to go to jail for it. But the question of such criminality is not an irrelevance for the United States. It matters for whether leaders in Washington can expect to gain cooperation in a military venture from key allies. It will affect the likelihood of US support for Security Council referrals in the kinds of situations that have been the focus of such referrals thus far. Foreign or international judgments not directly applicable to US actors could weaken the United States’ international standing and affect the trajectory of the law. And if the renewed attention to aggression facilitates a correction in refugee law jurisprudence, this could have direct implications for US troops convinced of the criminality of their state’s actions. In all these respects both for the United States and its allies, the crime of aggression matters.


Photo: Michael Mansfield QC, representing the group Legal Action Against War, holds press conference at House of Commons on March 2, 2004. The group asked the International Criminal Court to probe claims that British Prime Minister Tony Blair, Defence Secretary Geoff Hoon and Foreign Secretary Jack Straw committed war crimes in the invasion of Iraq – Ian Waldie/Getty