He earned his first law degree at John Casimir University in Lviv in 1939, leaving for the United States to take up a Harvard University research fellowship two weeks before Nazi Germany invaded Poland.

[1][2][3] As a protégé of Manley O. Hudson, he participated in the San Francisco Conference that established the United Nations, working on the statute of the International Court of Justice.

He was appointed an assistant professor there in 1951, succeeding Hudson to the Bemis Chair in 1961.

[4] The book called for complete disarmament and the use of world judicial tribunals to solve international disputes.

[5] Upon Sohn's death in 2006, UN Secretary General Kofi Annan issued a statement noting Sohn's reputation as "a voice of reason and source of wisdom," and celebrating his "firm belie[f] in the importance of the United Nations and of the rule of law in settling international disputes.