July 17, 1998, can be considered as one of the most important milestones of the international judicial structure: it is the day when the Rome Statute of the International Criminal Court was adopted by 120 states out of 148. Article 86 of Statute explicitly states that „States Parties shall […] cooperate fully with the Court in its investigation and prosecution of crimes within the jurisdiction of the Court.” As in the case of every international treaty, the principle of pacta sunt servanda enshrined in Article 26 of the 1969 Vienna Convention on the Law of the Treaties states applies, which explicitly states that “every treaty in force is binding upon the parties to it and must be performed by them in good faith.” As has been pointed out by the Permanent Court of International Justice, contracting states must make all the necessary internal measures which are required to fulfil its international obligations rising from a binding treaty. One could ask, why is this quite obvious argument important in the case of Hungary? Well, Hungary has ratified the Statute but still has not implemented it in its internal legislation. This can be considered as a serious constitutional omission, since if the Court would require the cooperation of Hungary – e.g. in the case of an arrest warrant – and it would not be able to fulfil it because of the lack of the internal legal norms, it would be considered as international legal responsibility of Hungary. In this article, I try to explore the reasons behind this omission and outline the possible solutions.