In the May issue of Reason magazine, Matthew Harwood reviews Hitler's American Model: The United States and the Making of Nazi Race Law. They learned from Jim Crow laws:
On June 5, 1934, leading Nazi jurists gathered for a meeting on Germany's "Jewish problem." They had one goal: to draft "unambiguous" legislation banning mixed marriages and sexual relationships. But they were split into two factions: the radicals, who wanted to criminalize miscegenation, and more traditional German jurists, who weren't sure this was workable. During the debates that followed, the radicals in the room repeatedly pointed to an example overseas: the United States of America. Uncle Sam and Jim Crow, they knew, had much to teach them.
In Hitler's American Model, a creepy work of comparative legal analysis, the Yale-based legal scholar James Q. Whitman argues convincingly that American jurisprudence—federal and state alike—provided both inspiration and a model for the most radical Nazi lawyers at the meeting. A little more than a year later, their discussions produced the Nazis' Citizenship and Blood Laws, known collectively as the Nuremberg Laws, which explicitly targeted Jews and separated them from the "true" German people, or volk.
The Law on the Protection of German Blood and German Honor, one piece of that legislation, criminalized sexual relations and marriage between a German and a Jew, defined as anyone with three or four Jewish grandparents. Jews who broke this law were punished with imprisonment or hard labor, sometimes both. Under the Reich Citizenship Law, Jews lost the status of citizen. Soon they were stripped of their political rights, including suffrage, as well. This is where the goose step toward the ovens of Auschwitz began.