Based on extensive empirical research, this ground-breaking book describes and analyses existing systems for enforcing sentences of imprisonment imposed by international criminal courts and makes recommendations for the strategic and structural development of the international penal system. In particular, it advocates a resocialisation-focused international penal policy delivered using restorative justice modalities post-conviction and the creation of an accountable international prison system. Singly or combined, these developments will contribute to the institutionalisation of the international penal system and enhance the international nature of the sanction, the international control over the way international punishment is enforced and the equal treatment of international prisoners. These developments will also help to ensure that international punishment is principled and progressive and implemented in a humane and effective system.