Hans Kelsen, the theorist and founder of the Vienna School who is well-known as “Einstein of Law”, is a notable lawyer who has a distinctive and exceptional character, and his views have been really effective on the process of developing international law debates. As a realist positivist, he has presented the pure theory of law and Monism which have been referred by other international lawyers for many years. One of the novel issues addressed by him is “the theory of international peace through law” and some parts of which have been affected by Immanuel Kant’s “PerpetualPeace”; but has been harmonized by means of some novelties in a specific form, with other theories of this Austrian-American scholar. It Is the author's opinion that Kelsen's internationalism and pacifism brought about anImportant turning-point In the theory of international law and anticipated by 50 years manyof the issues that the international community are today discussing: in particular, individualsas subjects of international law (and not only states) and the use of international criminaltribunals for the punishment of those responsible for war crimes and crimes againsthumanity. The author argues that there is some doubtwhether Kelsen's theoreticaland political goals. Finally,analysis and reviewing these theories clarify his providence and leadership in the international law debates.