The enforcement of sentences rendered by the international criminal courts and tribunals is quite distinct from the way in which prison sentences are enforced in domestic jurisdictions. The international criminal courts do not have a permanent prison at their disposal as their detention facilities were set up to hold only those awaiting trials or on trial. The tribunals are dependent on states to enforce their sentences. According to their Statutes the imprisonment is served in a state designated from a list of states that entered into a sentence enforcement agreement with a tribunal. The enforcement of international sentences is, in other words, “outsourced” to states willing to do so. The imprisonment is governed by the law of the enforcement state and subjected to the supervision of the tribunal.
In practice, international prisoners are scattered around different prisons across and within various countries (11 European and two African countries are enforcing international sentences). For this reason they are subjected to largely differing regulations and prison conditions and subjected to different daily regimes with varying emphasis on rehabilitation. It is not entirely clear what considerations, except for political factors, are taken into account when designating an enforcement state. The majority of decisions and communications within each tribunal and with individual states are confidential. For example, the ICTY has concluded enforcement agreements with 17 different European countries, with prisoners scattered across 13 of them. No country has been enforcing sentences for more than 6 ICTY convicts. On the other hand, the ICTR and SCSL have pursued a different designation strategy. The ICTR concluded 7 enforcement agreements with 3 African and four European countries. The vast majority of the ICTR prisoners are sent to 2 countries: Mali and Benin. The SCSL entered into an enforcement agreement with 4 countries. All its convicts (except of recently-convicted Charles Taylor who was transferred to the UK), however, are serving their sentences in Rwanda. The ICTR and SCSL prisoners are not only concentrated in a very limited number of countries but also serve their sentences in a special prisons or special wings interacting only with each other in contrast to the ICTY prisoners who are dispersed into domestic prison populations.
Why are these prisoners not sent back to their countries of origin to serve their sentences home? Since the conflict in the former Yugoslavia was still ongoing when the ICTY was established, countries of the former Yugoslavia were excluded from the possibility to enforce ICTY sentences. It has been argued, however, that since the circumstances have fundamentally changed, it should by now be possible to (also) enforce ICTY sentence in the countries of the former Yugoslavia, especially taking into account the possibility of the ICTY to transfer cases for trials to these countries.It seems that political reasons and the fear that the ICTY convicts will be accepted as war heroes with VIP treatment prevents this from happening. In contrast to the ICTY, the ICTR Statute explicitly includes Rwanda as one of the possible enforcement countries and in the SCSL Statute, Sierra Leone is even given preference to enforce the Court’s sentences. Only ‘if circumstances so require’, shall the individuals convicted by the SCSL serve their imprisonment in another willing state. In practice, none of the ICTR or SCSL convicts is serving his/her sentence in the country where (s)he committed crimes. The reasons for this range from security fears and the perceived inability of domestic prison authorities to prevent escape of international prisoners, to humanitarian considerations relating to conditions and the treatment of prisoners, such as overcrowding of prisons or insufficient sanitary conditions. Despite the fact that Rwanda has built a new prison facility - Mpanga prison - to ensure that ICTR convicts can serve their sentences in accordance with international standards, concerns have been raised that ICTR prisoners could spend their whole sentence in isolation in violation of their right not to be subjected to inhuman punishment. Currently, the prison is exclusively used to host the SCSL convicts and persons transferred from ICTR and third countries to face domestic prosecution in Rwanda.