This book thoroughly discusses the concept of sovereign immunity in international law and how the problems normally associated with the said subject can be resolved in order to promote justice. In part one, the author shows through a careful analysis of the law that restrictive immunity does not have vox populi in developing countries and that it lacks usus. He also argues that forum law, i.e., the lex fori is a creature of sovereignty and between equals before the law, only what is understood and acknowledged as law among states must be applied in as much as the international legal system is horizontal. Furthermore, the state never acts as a juridical or natural person and, therefore, in logical terms, its functions cannot be divided into potere politico and persona civile as a prelude to determine jurisdiction. The said Italian doctrine, therefore, is ex-facie erroneous, and that a simple dichotomy between absolute immunity and restrictive immunity wholly predicated on the nature test alone would not be helpful in promoting justice. Hence the contextual approach, arbitration and comparative dominant theory are suggested as essential tools to supplement the UN Treaty on state immunity when it comes into force because some states are likely to stay out of the said treaty regime. In part two, of the book, the author provides a comprehensive analysis of international criminal justice i.e., the prosecution of heads of state before international tribunals and the means or tools available to defend these leaders. To that end, it is apposite that a distinction between immunity ratione personae and immunity ratione materiae be made clear, whereby emphasis must be placed on their differences and legal consequences in regard to the verticality of international tribunals and foreign criminal jurisdiction of statese.g., the ICC and SCLC. The author further argues forcefully that the law has not changed and that despite the reforming zeal of some important states to change the law, in reality however, the law remains almost intact wholly structured on the presumption of immunity subject to certain limited acknowledged exceptions duly supported by opinio juris, thus eclipsing the suggestion by some scholars, senior courts and international tribunals that the law be instead based on an acknowledged exception to a presumed jurisdiction. This is because international law is a decentralized public order system without a compulsory jurisdiction.