In addition to his work on denazification, Karl Loewenstein participated in the redrafting of German laws. Unlike many of his colleagues, Loewenstein disputed the notion that the entire Nazi legal code was useless. He believed that many of the non-racist Nazi laws were useful, and that a return to the Weimar legal code, the code used before 1933, represented a retrograde course of action.
Loewenstein worked on drafts of the new marriage law, the law on the reorganization of the bar, the new civil service law, the law for the redress of National Socialist wrongs, and the new municipal code. Loewenstein also did a great deal of work on the first post-war German elections, as well as the reformation of German political parties.