This chapter follows the political and theoretical choices made by the Swedish law professor Karl Olivecrona. In 1940, following the publication of his main work, Law as Fact (1939), Olivecrona chose to take the side of Nazi Germany. Through a couple of pamphlets, one of them widely translated and distributed in occupied western Europe, Olivecrona argued for political adjustment to the ‘New Europe’ allegedly created by the Third Reich. Traditionally, this position has been explained by his allegiance to the radical neo-Kantian philosophy of legal realism. However, as pointed out in the chapter, his colleagues chose a completely different political path from the same philosophical foundations. Through a comparison between Olivecrona’s main principles and the legal philosophies of Hans Kelsen and Carl Schmitt—like Olivecrona, critics of legal positivism—it is instead suggested that the choice to support the Nazi war of aggression originated in a radical critique of the world order created after the Versailles Peace Treaty and a disbelief in the rule of international law. His was one of several choices in a world in turmoil, logically coherent with his legal theory but not its logical consequence.