Born in Hechingen, Province of Hohenzollern, in 1901, he received his law degree from the University of Berlin in 1928.
He was a research member of the Kaiser Wilhelm Institute of Foreign and International Law in Berlin until 1934, when he fled Germany to avoid Nazi persecution, as his wife, Eva Jonas, was Jewish.
[1] Kessler's most celebrated article, Contracts of Adhesion—Some Thoughts About Freedom of Contract,[2] elaborates the concept of "contrat d'adhésion" which originated in French civil law at the end of the 19th century and was introduced in American jurisprudence in a 1919 Harvard Law Review article by Edwin Patterson.
He argued that in such situations Eighteenth or Nineteenth Century concepts of freedom of contract were unrealistic and should be discarded.
[5] In his article, Natural Law, Justice and Democracy—Some Reflections on Three Types of Thinking About Law and Justice, Kessler maintained that the task of legal realism was "constantly testing out the desirability, efficiency and fairness of inherited legal rules and institutions in terms of the present needs of society.