Written for the forthcoming Oxford Handbook of the Theory of International Law, this chapter analyses the role of ‘theory’ in the field of international criminal law. It finds theory in international criminal law all over the place: theory is almost irrelevant whilst also highly influential; it is both explicated and covered up; it is developed but also immature. However, it is not just that the state of theory is all over the place; there is no shared understanding of what ‘theory’ in, or of, international criminal law refers to.
Theorising the concept of theory itself, the chapter identifies at least four types of ‘theories’ in international criminal law: (1) ‘factual theories’ (theories of a case); (2) ‘operational theories’ (mental schemes that the field employs in its operations, for instance to organise modes of liability, systematise crimes, or classify sentences); (3) ‘foundational theories’ (systems of ideas about the origins, essence and rationales of the field); and (4) ‘external theories’ (theories that try to make sense of international criminal law as a phenomenon, and study the meaning and effects of the field as a whole beyond its stated objectives, usually from a perspective external to international criminal law).
Theorising international criminal law is not exclusive to scholars or practitioners: international criminal law is also ‘theorised’ by millions of people who, without considering themselves to be ‘theorists’ or ever using the word ‘theory’, try to make sense of international criminal law as they encounter it in their daily lives. As a result, in addition to the axis along which we find factual, operational, foundational and external theories, we can also identify a further axis, with ‘official’ and ‘popular’ theories at its ends.
It is usually when the different types of theories in international criminal law are considered in light of each other that theoretical weaknesses are revealed and, on that ground, the field is labelled as ‘under-theorised’. Perhaps the greatest disconnect is between the official and the popular theories. Tribunals increasingly pay attention to ensuring that the official theories (in particular, the foundational theories) inform the general public’s views, especially in countries where international criminal tribunals intervene. Far less attention, however, is being given to ensuring that popular theories are fed back into the official theories, which in fact have much to gain from connecting with the day-to-day experience of international criminal law. However, for that to happen, official theories of international criminal law must first recognise popular theories as valuable.