International criminal proceedings have been consistently criticized due to the lack of an international legislative system, mandatory competent courts, and organized enforcement mechanisms. These factors are essential for establishing a comprehensive and credible legal framework. These shortcomings were particularly evident during the Nuremberg and Tokyo trials, where reliance on the concept of "justice" could not fill the void left by the absence of "legality." The criticisms raised during and after these trials highlighted the importance of the principles of legality of crimes and punishments within international criminal law. Although the process of accepting and establishing these principles has been slow, it has progressed steadily. A historical examination of international criminal proceedings—from the Leipzig High Court in the early 20th century, the Nuremberg and Tokyo trials in the mid-century, the International Criminal Tribunals for the former Yugoslavia and Rwanda in the 1990s, and ad hoc tribunals like the Special Court for Sierra Leone to the International Criminal Court (ICC) at the beginning of the 21st century—demonstrates a profound and gradual evolution in the acceptance and implementation of the principles of legality of crimes and punishments. This process began with denial and initial indifference to these principles and ultimately reached a point where adherence to them was explicitly stated as a legal necessity.