When the Rome Statute of the International Criminal Court was being negotiated, there was much discussion about whether ‘treaty crimes’ should be included within the jurisdiction of the Court along with the ‘core crimes’ of genocide, crimes against humanity, war crimes, and the crime of aggression. Ultimately, only the ‘core crimes’ were included. In the context of that debate, ‘treaty crimes’ referred to serious drug crimes as contained in United Nations treaties on the subject, and the set of ‘terrorism’ offences contained in a number of multilateral treaties entered into from the 1970s onwards, beginning with hijacking and other offences against aircraft. The dozen or so terrorism treaties in question were negotiated under the auspices of the United Nations and its specialised agencies, notably the International Civil Aviation Organisation and the International Maritime Organisation. These terror crimes include assaults on internationally protected persons, the taking of hostages, unlawful dealings in nuclear materials, violence at airports serving international aviation, acts against the safety of maritime navigation and on fixed platforms on the continental shelf, attacks on United Nations and associated personnel, terrorist bombings, the financing of terrorism, and nuclear terrorism. Such crimes may yet find their way into the jurisdiction of the Court, since it was understood in Rome in 1998 that their inclusion would be considered ‘later’. The process for their possible inclusion is proceeding at a glacial pace and ‘later’ is nowhere near in sight.

I suggest in this chapter that the category of treaty crimes is in fact much broader than those that were on the table in Rome. It encompasses a multitude of infractions from the exotic to the mundane that have been regulated in bilateral and multilateral treaty practice over the last two hundred years. It is common these days to describe this area as ‘transnational criminal law’, as opposed to ‘international criminal law’ or ‘international criminal law stricto sensu’, the latter terms being commonly used to describe the Rome Statute crimes. The treaties that are the subject of this chapter are often labelled ‘suppression conventions’, a descriptor which emphasises their core feature. That core is a promise by the parties to make something criminal under their domestic law, to ‘suppress’ it.