Thus, heads of state, senior state officials, and diplomats were immune from any examination of their conduct by other states. However, it was also expected that heads of states and senior state officials who could do nothing wrong would present acceptable standards of conduct at all times. Within the relatively recent past, the concept of state immunity in international law has changed because sovereign states have demonstrated that they are capable of gross violation of human rights and massive wrongdoing. The First and Second World Wars present a historical testimony for what can happen when heads of state and senior state officials indulge in morally unacceptable conduct. This brief essay presents a discussion about state immunity from proceedings alleging jus cogens norms.Even in the nineteenth century, the principle of ‘Supremacy of State Sovereignty’ was recognized under the prevailing international law regime and despite the numerous wars the doctrine of ‘Equality of States’ was also well established. 1 International law considered a state as being inviolable and it had absolute jurisdiction over all persons and all things within its territory, with a wide-ranging right to pursue its interests. Thus, sovereigns were immune from criminal prosecution in the courts of another state because they represented the will of the state. It was not possible to charge heads of state with criminal conduct while they were in power. State actors and legal scholars considered the previously mentioned rules as being beyond controversy. Also, all states were equal regardless of the size of their territory or strength and this meant that their heads of state and senior government officials enjoyed the same immunities. However, even in the nineteenth century, the notions of sovereign immunity and protected sovereignty were being challenged by stronger nations and colonial powers.