In international life, decision makers face difficult problems on a regular basis. What should decision makers do, for instance, when international rules that ‘promote minimum world order and universally-desired values’ run counter to, or threaten, ‘basic values or essential interests of communities’ that those decision makers serve (p 2)? Are decision makers entitled to disregard, or disobey, such international rules, or must they comply with them?

This is the immensely practical but also theoretically complex question confronted by Professor Cheng in his book, When International Law Works: Realistic Idealism after 9/11 and the Global Recession. For Professor Cheng, such difficulties cannot be resolved by the persistent debate as to whether ‘international law is really ‘‘law” ’. He is highly critical of that debate, and dismisses those who continue to engage with what David Harris describes as a ‘standard sherry party question’ (David Harris, Cases and Materials on International Law (7th edn, Sweet & Maxwell 2010) p 5) as not providing ‘all the reasons for obedience or disobedience’ (p 2). Cheng sees the real issue as being ‘what decisionmakers should do about international law, whether or not it is law’ (p 2). The book addresses this issue through the lens of various ‘decisionmakers’, being international judges (chap 4), arbitrators (chap 5), regulators (chap 6), legal advisers (chap 7) and officials (chap 8).

The essential thesis of the book is that when such decision makers disobey international law, they ‘ought not to claim a unique exception for themselves’, as that only serves to encourage others to follow suit and act inconsistently with the relevant rule; rather they should ‘explain their reasons for disobedience’, in order to permit other decision makers to decide if those reasons have any validity, and expectations of appropriate conduct for the future can be adjusted (p 2). Professor Cheng refers to this as a ‘justificatory framework to help decisionmakers consider relevant prescriptions and what they ought to do’ (p 13). The approach is described as ‘justificatory’ as it will assist in ‘shaping the international legal system to more effectively achieve good outcomes in international problems and to provide reasons to promote and obey prescriptions’ (p 13). In particular, in providing reasons for complying or not complying with a particular rule, decision makers can avoid ‘arbitrary feedback loops’ (p 15). Professor Cheng argues that ‘[t]his process can help adjust the international legal system to contemporary realities while avoiding unjustified disobedience and disruptions’ (p 2). It is key to the book's thesis that law is characterized as an ‘interpretative process intertwined with morality’ (p 16); this approach is perhaps unsurprising, as Professor Cheng is a product of the New Haven School, having studied under Professor Reisman at Yale University.

In the book, Professor Cheng provides a stimulating review of the various theories on the nature of international law and an interesting examination of the roles of various decision makers and the competing considerations they must take into account. He also offers a fresh perspective on the debate most recently revisited by Jack Goldsmith and Eric Posner (The Limits of International Law (OUP 2005)), Andrew Guzman (How International Law Works: A Rational Choice Theory (OUP 2007)), and Mary Ellen O'Connell (The Power and Purpose of International Law (OUP 2008)), arguing that it is more productive to ask what decision makers should do about law, than what law requires of decision makers (p 296). There is much to comment on from the various case studies, and although Professor Cheng claims to take a politically moderate view (p 16), some will have their eyebrows raised by, or take exception to, his extensive criticism of the International Court of Justice's judgment in the Nicaragua case (pp 141–62); the suggestion that the award of the NAFTA tribunal in Loewen v United States is in part defensible as it ‘reduc[ed] the risk that the United States would withdraw from NAFTA’ (p 191); or the view that the practice of water-boarding does not violate the customary international law prohibition on torture (p 238). Clearly, we live in a world where decisions, and justifications for those decisions, do not come easily, and there is much to discuss. But in the limited space available for this review, I propose to consider Professor Cheng's application of the justificatory framework to international judges (chap 4), and offer a brief comment on two points.

In this chapter, Professor Cheng first sets out what he considers to be the judicial function, which is the settlement of international disputes, and the clarification and development of international law (pp 122–3). He then argues that although judges have a duty to apply international law ‘using legalist reasoning and procedures’ (p 124), ‘legalism alone should not control outcomes in adjudication’ (p 125), but that judges must also take into account questions of ‘morality’ and ‘effectiveness’. On the relevance of ‘morality’, he explains that ‘[w]here legalism does not resolve interpretative ambiguity, judges ought to supplement legalism with moral reasoning’, although this is to be done ‘within legalist limits’ (p 125). This has intuitive appeal in the international legal system, which typically lacks adjudicatory and enforcement mechanisms, but it also raises a number of questions; why should any ambiguities in the applicable rules not be resolved by, for instance, the rules of treaty interpretation in the Vienna Convention on the Law of Treaties; or if ambiguities persist, why should such gaps or instances of silence not be filled by the application of general principles of law? It may be (indeed, it is hoped) that one will arrive at the same destination, but it seems that choosing the route more clearly grounded in the application of rules is to be preferred. If there is a genuine non liquet, policy considerations will of course become relevant, but the Advisory Committee of Jurists’ purpose in including ‘general principles of law’ in Article 38(1) of the Statute of the Permanent Court of International Justice was to avoid this being a possibility.

As for considerations of ‘effectiveness’, the notion that ‘[j]udges should also be concerned about the effectiveness of their decisions because a decision that is ignored is useless’ (p 131) is likely to raise the hackles of those who seek international justice (which, to be fair, Professor Cheng acknowledges at pp 132–3). The outcome in the Nuclear Tests cases offers a sharp reminder of this. It is recalled that Australia and New Zealand had sought a declaration from the International Court of Justice (‘ICJ’) that France's programme of atmospheric nuclear testing in the South Pacific was ‘not consistent with applicable rules of international law’, and an order that France would not carry out any future tests (see eg Application Instituting Proceedings, in Nuclear Tests Cases (Australia v France), ICJ Pleadings, Oral Arguments, Documents, vol I, pp 14–15). As is well known, the ICJ ultimately ruled that Australia and New Zealand's application had become ‘moot’ in light of France's cessation of its atmospheric nuclear testing programme, and determined that the claim was therefore inadmissible (Nuclear Tests [1974] ICJ Reports pp 269–72). This was criticized in some quarters as an abdication by the ICJ of its judicial functions; arguably, a dispute persisted as to the legality of the past nuclear tests carried out by France, even if no order would be required as regards future testing. It might be thought that the ICJ simply chose the path of least resistance, preferring to avoid rendering a judgment that might have been ignored by France, in the event that the ICJ made a finding of unlawful conduct (it is further recalled that France did not appear in the proceedings). Does the justificatory framework support the outcome in the Nuclear Tests cases? In a more extreme example, one can refer to the ICJ's advisory opinion in Legality of the Threat or Use of Nuclear Weapons, in which it (in)famously held that ‘in view of the current state of international law, and of the elements of fact at its disposal, the Court cannot conclude definitively whether the threat or use of nuclear weapons would be lawful or unlawful in an extreme circumstance of self-defence, in which the very survival of a State would be at stake’ (para 105(E)). Professor Cheng's justificatory framework would appear capable of explaining this outcome, but the difficulties posed by this case were palpable.

Professor Cheng has offered a fresh perspective on the role of international law in international affairs which is to be warmly welcomed. The justificatory framework should, in general, serve to advance our ability to grapple with the difficult questions of how international law fits into the decision-making process. We also need to remember that international relations is not a space that is necessarily ‘owned’ by lawyers, a point that was recently made by Sir Daniel Bethlehem QC (‘The Secret Life of International Law’, Address to the Lauterpacht Centre of International Law, 20 January 2012). There are many challenges to be met, and there will be more hiccoughs along the way. But Professor Cheng's contribution provides an interesting view that takes us further forward.