This article discusses the development and usage of Head of State Immunity in International Law. The Basis of Head of State Immunity is examined with a focus on the Theories of Representative Character and Functional Necessity. It also defines the two types of Immunity; Functional and Personal Immunity. The paper extensively discusses the different measures taken to limit the scope of Head of State Immunity, which includes; the Versailles Treaty, Nuremberg trials, the Pinochet Case and the Arrest Warrant Case also the immunity of Heads of State before the International Criminal Court (ICC) and Relationship between Applicability of Heads of State Immunity and most International Crimes and the crimes that fall under the purview of the International Criminal Court. The major issue of concentration is whether Heads of State can still enjoy Immunity after committing International Crimes which falls under the Jurisdiction of the International Criminal Court. The paper aims to ascertain the extent to which Heads of State in office enjoy from Jurisdiction for International Crime. The methodology used in the paper is doctrinal; basically, from secondary sources that includes journals, online articles and textbooks. The paper concludes that the once impressive protection afforded to Head of State has eroded dramatically over time. Immunity cannot be sought before all International Tribunals, according to the International Criminal Court, under a new concept of Customary International Law, expressed in Article 27 of the Rome Statute of the ICC