[1] Prior to World War II, Fraenkel served as a criminal defense lawyer for Jews who were targeted by the Nazi regime.

In 1939 he immigrated to the United States where he began to develop his respect for the politics of that country, especially its pluralism and its checks and balances.

He wrote his dissertation in law about The void labour contract (Der nichtige Arbeitsvertrag), under Hugo Sinzheimer.

[4] During the Weimar Republic he worked as a lawyer for labor law with Franz Leopold Neumann, published scientific publications and was engaged in socialist politics.

For Fraenkel there coexisted in the Nazi government a "normative state" (Normenstaat), which secured the continuation of capitalist society for those Germans not threatened by Nazism, and a "prerogative state" (Maßnahmenstaat), which used both legal and extralegal violence against people considered to be enemies of Nazism and Nazi Germany.