I have posted the essay on SSRN. Here is the abstract:
The question “what is an international crime?” has two aspects. First, it asks us to identify which acts qualify as international crimes. Second, and more fundamentally, it asks us to identify what is distinctive about an international crime – what makes an international crime different from a transnational crime or an ordinary domestic crime.
Considerable disagreement exists concerning the first issue, particularly with regard to whether torture and terrorism should be considered international crimes. But nearly all states, international tribunals, and ICL scholars take the same position concerning the second issue: an act qualifies as an international crime if – and only if – that act is universally criminal under international law. The international-law aspect of the definition distinguishes an international crime from a domestic crime: although some acts that qualify as domestic crimes are universally criminal – murder, for example – their universality derives not from international law, but from the fact that every state in the world has independently decided to criminalize them. The universality aspect of the definition, in turn, distinguishes an international crime from a transnational crime: although a transnational crime such as drug trafficking involves an act that international law deems criminal through a suppression convention, international law does not deem the prohibited act universally criminal, because a suppression convention does not bind states that decline to ratify it.
This definition of an international crime, however, leads to an obvious question: how exactly does an act become universally criminal under international law? Two very different answers are possible – and the goal of this article is to adjudicate between them. The first answer, what I call the “direct criminalization thesis” (DCT), is that certain acts are universally criminal because they are directly criminalized by international law itself, regardless of whether states criminalize them. Nearly every modern ICL scholar takes this position, as does the ILC.
The second answer, what I call the “national criminalization thesis” (NCT), rejects the idea that international law bypasses domestic law by directly criminalizing particular acts. According to the NCT, certain acts are universally criminal under international law – and thus qualify as true international crimes – because international law obligates every state in the world to criminalize and prosecute them. No modern ICL scholar has taken this approach, although intimations of it date back to Grotius.
Which thesis is correct? This article argues that it depends on whether we adopt a naturalist or positivist approach to international law. Although every international criminal tribunal has insisted that international crimes are positivist, not naturalist, phenomena, no extant theory of positivism – not even so-called “instant custom” – is capable of justifying the idea that certain acts are directly criminalized by international law. On the contrary: if we take positivism seriously, the NCT provides the only coherent explanation of how international law can deem certain acts to be universally criminal. Maintaining fidelity to the DCT, therefore, requires rejecting positivism in favour of naturalism – with all of naturalism’s inherent limitations.
I have given a number of talks on this topic over the past couple of years, and my positivist critique of direct criminalisation has always proved controversial. The argument in the essay has evolved substantially, but I doubt it will be any more popular. I still continue to be surprised that, with the exception of a somewhat skeptical Roger O’Keefe, no scholar and no court has ever attempted to provide a comprehensive defence of the idea that certain acts (international crimes) are directly criminalised by international law. The idea is simply taken for granted based on a single statement in the IMT judgment and on the work of the International Law Commission. Indeed, as I try to show, direct criminalisation seems to be little more than an article of faith — a naturalist artifact that has proven very useful for the ICL project, which is predicated on the superiority of international law over domestic law. Indeed, my suspicion, merely noted in the essay, is that ICL is inherently naturalist, at least in the form that has the kind of sovereignty-limiting muscle its acolytes believe it should have.
The essay is very long — 30,000 words, nearly 400 footnotes. I’ve submitted it for consideration by AJIL, but I am sure I will revise it substantially before it is ultimately published there or somewhere else. So comments and criticisms are, as always, most welcome.