In the decades that passed since World War II, significant developments have taken place in international law. The main developments are the establishment of the tribunals in Nuremberg and Tokyo, the Geneva Convention and its complementary protocols, and the establishment of the tribunal for the prosecution of war crimes in Yugoslavia and Rwanda. Very often, norms are applied retroactively in the prosecution of war criminals at those tribunals. As a result, the courts had to find various justifications for violating the principle of legality, namely, the imposition of criminal sanctions on acts that were not criminal at the time they were committed.
On July 17, 1998, at the end of a month of deliberations, 120 countries ratified the treaty of the International Criminal Court (also known as the "Rome Statute"). On July 1, 2002, following the UN resolution, the court's constitution came into force, and for the first time in the history of international law, the international community founded a permanent International Criminal Court.