While the international legal rights and obligations of non-state actors continue to increase, states are undoubtedly still the front-line responders to today's terrorist threats so that any effective action to prevent terrorism requires the cooperation of responsible states. There have, consequently, and particularly since the events of 11 September 2001 (“9/11”), been efforts to enhance the capacity of states to exercise their sovereignty responsibly. It is in this light that this work seeks to offer a new perspective as to how this might be achieved through utilising the law on state responsibility.

The topic of state responsibility for transnational terrorism is far from new. Notable recent additions to the burgeoning literature in the field include Tal Becker's Terrorism and the State: Rethinking the Rules of State Responsibility (Oxford 2006) and Kimberley Trapp's State Responsibility for International Terrorism: Problems and Prospects (Oxford 2011). This work is a noteworthy contribution to the existing literature mainly through its proposal for a “strict-liability infused model” in connection with states’ indirect responsibility for failing to abide by their counter-terrorism obligations. Indeed, the proposal for such a strict-liability form of responsibility as “a new theory of prevention” is the book's main contribution to solving the enduring problem of preventing terrorism. More specifically, the author proposes a two-tiered model so that “once a terrorist attack has been launched from a State's territory, that State becomes automatically indirectly responsible for the excursion” (pp. 229–230) with the burden then upon it to demonstrate how it acted with due diligence in any steps it took to prevent the attack. As Proulx argues, “[t]he objective in shifting the onus is not only to transfer the burden of proof but also to shift the incentives to host-States” (p. 229).

This proposal is not without its merits. In particular, and as the author recognises, “[t]he most convincing argument for the implementation of strict-liability dimensions resides in the evidentiary problems pertaining to the establishment of attribution” (p. 220). With some often vague and malleable preventative counter-terrorism obligations combined with the need to gather evidence of the host state failing to act with due diligence, holding wrongdoing states responsible is not easy for an injured state or the international community. As a consequence, “[w]hen faced with the breach of the obligation to prevent terrorism, an aggrieved State is often at a legal impasse in establishing the host-State's responsibility. Undoubtedly, the host-State is often better positioned than the injured State to know what logistical and human means, intelligence, police and military means were at its disposal to eliminate the threat” (p.221). This, in itself, is difficult to disagree with. There are, however, some notable problems with the methodology and supporting framework of the central proposition advanced in the book.

In Part I of the book the author, presumably to make his strict liability model more palatable, claims that there has been a significant shift since 9/11 in state and institutional practice from holding states directly responsible, through the attribution of acts of international terrorism to them thus opening up the possibility for the victim state to invoke its right of self-defence against the host state, to holding them indirectly responsible, through the state somehow failing in its obligations to prevent, or at least act with due diligence in trying to prevent, the terrorist group from operating and carrying out the attack. After 9/11, the author argues, state support of a more passive nature “seems to have achieved international precedence over the general concept of attribution” (p.175).

While there has indeed been much attention on the prevention of, and indirect responsibility for, terrorism in the aftermath of the 9/11 attacks, there has been an equal – and perhaps, at least in the context of scholarly contributions, greater – focus upon the occasions when attribution might be said to exist, particularly in the context of a state invoking its right of self-defence against another state following a terrorist attack. In any case, while the author claims that the International Law Commission's Draft Articles on Responsibility of States focus too much upon the need for attribution through state control of non-state actors, the Articles equally hold that “[e]very internationally wrongful act of a State entails the international responsibility of that State” (Article 1 (emphasis added)), thus permitting states which do not abide by their counter-terrorism obligations to be held indirectly responsible for a terrorist attack which perhaps occurred partly as a result of the state's failings. Ultimately, it seems, at least at first, somewhat unnecessary for the author to establish such a shift so as to substantiate his central point regarding the incorporation of a strict-liability model in the context of indirect responsibility.

In practice, the only context in which the distinction between these different modes of responsibility becomes relevant is in determining the types of consequences that the responsible state is required to face or the responses that the victim state is permitted to take. More specifically, whether a forcible response can be undertaken in response is in practice the most controversial, and arguably important, issue in distinguishing between the two modes of responsibility. It is in this light that Proulx's assertions regarding the shift from direct to indirect responsibility begin to take on relevance as it becomes clear that the claim is being made that, in contrast to the formal position set out above, indirect responsibility now opens up the possibility for a forcible response against host states. This argument is not expressly asserted in the book, mostly because, and somewhat surprisingly, Proulx does not give much attention to the permissible responses to a finding of each form of responsibility and, in particular, consciously excludes any real discussion of self-defence, or indeed any other forcible responses, upon the basis that it is a “self-contained and analytically distinct international legal category” (pp. 75–6). However, the point is nonetheless made that indirect responsibility “should not merely be reduced to an alternative route and could, arguably, supplant the direct responsibility paradigm altogether in many cases. For one thing, that posture would partly do away with the legal and political pitfalls associated with branding states ‘directly’ responsible” (p. 103).

However, the collapsing of the distinction between direct and indirect responsibility in this way firstly ignores why the distinction exists. Although a close enough nexus between the non-state actors involved and the host state so as to give rise to direct responsibility may, as the author is keen to point out, be difficult to prove, this is understandable seeing that it gives rise to the possibility for a forcible action in self-defence against the host state – the most severe of consequences. Secondly, the distinction between direct and indirect responsibility is very much maintained in state practice, contrary to what Proulx claims. In its response to the 9/11 attacks the US accused the Taliban of “harbouring” al-Qaida. While accusations of a similar nature have in the past led to states, perhaps most notably Israel, taking action against the actual non-state perpetrators of the attacks within the harbouring or supporting state, on this occasion the US used the harbouring of al-Qaida by the Taliban as the basis for holding the Taliban, and in that sense the state of Afghanistan, responsible for the attacks and consequently targeting it and its infrastructure in self-defence. Under the traditional formal view of the law, without attribution having been established through the Taliban actually controlling al-Qaida, a forcible response would not have been permissible and in this sense the actions and associated justification of the US represented a blurring of the distinction between direct and indirect responsibility.

The author uses the fact that the actions of the US and the justification for them were well accepted within the international community at the time to make the argument that there has been a shift from direct responsibility to indirect responsibility, albeit with the same possible responses to the victim state. Where the real problems come is in the author's failure to adequately grapple with the state practice subsequent to the 9/11 attacks. In this light, the widespread acceptance of the US's response within the international community at the time of the 9/11 attacks, whether based upon legal or political grounds, has to be seen as sui generis. Indeed, if one is open to the nuances involved in this practice it reveals that, rather than following the precedent set by the US in its response to 9/11, states have, while often labelling a state as a “harbour” for the non-state perpetrators of the attack, nonetheless restricted their response to forcible action against the non-state actors themselves, albeit within the harbour state, as opposed to targeting the harbour or host state and its associated infrastructure. This can be seen in, for example, Russia's action against Chechen rebels in Georgia in 2002, Israel's strikes against Islamic Jihad in Syria in 2003 and against Hezbollah in Lebanon in 2006, as well as Columbia's targeting of Farc members in Ecuador in 2008. While significant weight is given to subsequent state practice in Part I of the book, the author ultimately fails to assess the significance of this practice and, in doing so, to make the important distinction between a forcible response against a host state itself and a forcible response solely against the non-state territorial actors within a host state.

The distinction between these two scenarios is important as it is difficult to think of the former – with the victim state actually attacking the harbouring or host state perhaps resulting in a regime change as per the response to 9/11 – as representing anything other than the victim state holding the host state itself in some way directly responsible for the attacks and the activities of the terrorist actors upon the host state's territory. Indeed, a potential widening of the concept of attribution to facilitate a finding of direct responsibility in such circumstances, and thus a response in self-defence, is how the academic literature has generally framed it, as opposed to broadening, and in a sense reconceptualising, indirect responsibility in this context. On the other hand, and on the basis that there is no consent for the anti-terrorist operation by the victim state, violating a harbouring or host state's territory in order to attack solely the non-state terrorist actors themselves on the basis that the host state was unable or unwilling to do anything about their activities, appears to be more accurately a finding of indirect responsibility. Indeed, the victim state is responding in self-defence only against the actual perpetrators of the attack. The necessary negative side effects of such a response, in particular a violation of the host state's territory, are thus justified upon the basis of the host state being indirectly responsible in failing for one reason or another to prevent the activities of the terrorist actors, or even simply because the actions in self-defence which take place upon the host state's territory are deemed “necessary” under this particular customary international law requirement.

Lastly, if the author is then seeking to make such indirect responsibility and the ensuing consequences – possibly of a forcible nature – automatic under the strict-liability infused model put forward in Part II of the book, then it is difficult to see this lex ferenda argument having any real prospects of taking its place as lex lata. Automatic attribution of a terrorist attack upon its occurrence to a host or harbouring state, thus opening up the right of the use of force in self-defence, would, for obvious reasons, prove enormously controversial and has consequently not been seriously suggested elsewhere as a way forward. Indeed, given the implications for individual states, and the reversal of the burden of proof in this context to “guilty until proven innocent”, it is very unlikely that the necessary state practice and opinio juris would be generated.

In conclusion, Transnational Terrorism and State Accountability: A New Theory of Prevention is a remarkably ambitious work that is both meticulous in its research in many aspects and engages to a large extent with both the legal and policy issues involved in its arguments. Any issue that one may take with the book should not detract from the overall progressive nature of its central propositions, which can only trigger further discussion and debate. Such contributions to tackling enormously complex issues such as preventing transnational terrorism should be welcomed and the current reviewer would encourage academics of various disciplines, practitioners and, perhaps most importantly of all, policy makers, to engage with these particular ones.