Hans Kelsen
Kelsen's is considered a very strict and scientifically understood type of legal positivism. It is based on the idea of a Grundnorm, a hypothetical norm on which all subsequent levels of a legal system such as constitutional law and "simple" law are based. For Kelsen, "sovereignty" was a loaded concept: "We can derive from the concept of sovereignty nothing else other than what we have purposely put into its definition."
His theory has disciples among scholars of public law worldwide. His disciples developed "schools" of thought to extend his theories, such as the Vienna School in Austria and the Brno School in Czechoslovakia. In English-speaking countries, H. L. A. Hart and Joseph Raz are perhaps the most well-known authors who were influenced by Kelsen, though both differed from Kelsen's theories in several respects.
Read more about this topic: Legal Positivism, History