For various reasons, Glaser must be understood as a significant scholar of international criminal law. Already in the 1920s, he wrote about the idea of international criminal justice and the creation of an international criminal court. He devoted his main research after World War II to this emerging discipline. He was the first academic who collected various forms of sources and opinio juris to give scholarly support for the development of a new discipline of ICL to be studied at institutions of higher education. At the same time, Glaser was a lawyer involved in some of the political and judicial turmoil of his times especially in Poland. He supported and represented the repressed members of Poland’s political opposition before Polish courts before World War II, he also fought against impunity for grave crimes through his work in the UNWCC during the war, and he provided advice on the draft for the Convention on the Non-Applicability of Statutory Limitations for Grave Crimes.