Just Security and Chatham House are hosting a “mini forum” to debate and discuss Chatham House’s new research paper on “Aiding and Assisting: Challenges in Armed Conflict and Counterterrorism.” This series includes contributions from Harriet Moynihan, Shaheed Fatima, Ryan Goodman, and Alex Moorehead. Stay tuned for more from them and others who may join.

I am grateful for the opportunity to comment on Chatham House’s Research Paper, “Aiding and Assisting: Challenges in Armed Conflict and Counterterrorism.” At the outset, let me add my congratulations to Harriet and the International Law Programme at Chatham House. The Research Paper is clear and engaging, and distills the complicated normative terrain into its essential elements. Moreover, its prescription of strategies and recommendations for reducing risk of wrongful assistance has the potential to make a real contribution to state compliance with a range of primary rules of international law.

In this brief post, I wish to make three points, two of which serve as background to the paper as a whole and one that picks up on a question raised but not pursued therein. These concern the structural significance of the rule on aid or assistance in Article 16 of the ILC’s Articles on Responsibility of States for Internationally Wrongful Acts (ARSIWA); the disjuncture between the (formal) legal heritage of the rule and its importance; and the relationship between complicity in the law of state responsibility and complicity in international criminal law.

As to the first, the structural significance of the rule in Article 16 ARSIWA lies in its generality, or to be more precise, in its double-generality. Prior to the entrenchment of Article 16, international law recognized certain rules that might be thought as specific complicity rules. These could be specific in terms of the forms of complicit conduct prohibited and/or in terms of the principal wrong onto which the prohibition on complicity grafted. By contrast, as the Research Paper points out, Article 16 (i) covers all forms of assistance and (ii) applies in respect of any principal wrongful act, so long as that act would be wrongful if committed by the assisting state. This double-generality is the key to Article 16.

As to the second, it is worth dwelling on Article 16’s heritage and impact. Here, we can connect two threads. On the one hand, there is the widely noted point that Special Rapporteur Roberto Ago understood his initial introduction of the rule into ARSIWA be a matter of progressive development – an understanding probably justified by the practice at that time. On the other, once adopted Article 16 benefited from what David Caron calls the paradoxical relationship between the form and authority of the ILC’s text and what James Crawford terms international lawyers’ thirst for standards. Article 16, like many other of the ILC’s Articles, has been ‘received into customary international law heaven without the intermediate purgatory of a diplomatic conference or Sixth Committee working group.’

With these two points in mind – the emergence of a new and structurally significant rule – it is no surprise that the entrenchment of Article 16 has provoked the many difficult questions raised by the Research Paper. These include how it relates to other primary rules of international law, what kinds of contribution are sufficiently proximate to give rise to responsibility, and how preventive measures might exculpate assisting states. In a sense, the rule is still working its way into practice. Moreover, complicity doctrine is notoriously difficult in domestic criminal law and international criminal law, and is receiving increasing attention in private law. Questions of accessorial liability are inevitably complex.

As to my third point, I suggest that complicity is a useful lens through which to think more generally about the relationship between individual criminal responsibility and state responsibility arising out of the same factual matrix. Take a situation where the provision of weapons by state officials of State A to state officials of State B facilitates the commission of war crimes. Here, there is the potential for concurrent responsibility: state responsibility for assistance under Article 16 and individual criminal responsibility for aiding and abetting under international criminal law. The crucial question is how those two bodies of law relate to each other.

In thinking about this question, two claims seem right to me. It is not necessarily the case in this situation that the elements of the rule on complicity in international criminal law are identical to those in the law of state responsibility. As the Research Paper notes, these are “different areas of international law with different histories and characteristics.” Here, the potential difference in the two complicity rules is a specific iteration of a possible wider divergence between rules establishing individual criminal responsibility and state responsibility. As Gaeta has argued, the two forms of responsibility may be “triggered by the violation of non-identical primary rules.”

Having said that, if the elements of the respective rules on complicity do (or are to) diverge, it would be surprising if those relating to state responsibility were more restrictive than those relating to individual criminal responsibility. In both cases, the elements of the rules must be informed by the nature of responsibility and the capacities of the respective subjects. Thus, for instance, rules relating to individual criminal responsibility must be informed by a set of considerations demanded by their penal nature. At present, the fault element of the complicity rules on both levels is contested. Leaving that aside, it is possible to imagine that the fault element of the rule in Article 16 will evolve in customary practice to encompass situations in which it would be illiberal to impose criminal responsibility on the participating officials. Here, a participating official’s attributable conduct might give rise to state responsibility under Article 16 without giving rise to individual criminal responsibility for aiding and abetting. A cleavage in that direction seems more likely than the reverse.

The relationship between complicity in international criminal law and state responsibility is only one issue in this area that requires further thought; the research paper raises many others. More generally, it sets out with admirable clarity the legal framework and possible strategies for states to mitigate their risk of wrongful conduct.