The Nazi German legal system is actually a fascinating topic. There was a famous debate between probably the two biggest academic names in jurisprudence of the last century about whether it could be accurately characterised as system of laws at all. These were in articles published by Lon Fuller and HLA Hart in the Harvard Law Review.

Fuller said that because of things the Nazi regime with its legal system did like creating retrospective laws (e.g. it something was not illegalwhen you did it, but they create a backdated law then arrest you for it anyway), immoral laws, and questions about influence on judges it should be seen as not really law at all.

Hart looked at other factors, such as the fact the formalities of the law were generally followed (with inconvenient laws being changed rather than ignored, for example) and argued it was just a bad legal system, but still should be considered law.

A particularly interesting example that illustrates both the implications of the debate about Nazi Germany and the sort of laws that existed is the 'Grudge Informer' case.

Basically a woman was angry at her husband and informed on him to the police for slandering Hitler. He was sentenced to death, sent to the front but managed to survive. She was prosecuted after the war. Her argument in court was that she merely acted in accordance with the law, as he really did slander Hitler. The German court held that those laws were contrary to natural justice and not valid, affording her no defence, and she was convicted.

My personal view is that the post-war court had it wrong and that the Nazi legal system was a 'real' legal system in the Hartian sense, just one with laws that were terrible from a policy perspective.

I know people will say that the Nazi regime was so immoral you shouldn't recognise its laws as valid. One argument against this (anti-positivistic) approach I heard made by Bernhard Schlink, a german judge and novelist (at a speech I attended, so no source) is that the German judges under the nazi regime who took a strict legalist approach were actually most effective at resisting Nazi influence because their approach led them to enforce laws that were often inconvenient for the Nazi regime.

Sources:

71 Harv. L. Rev. 630 (1957) Positivism and Fidelity to Law--A Reply to Professor Hart; Fuller, Lon L.

83 N.Y.U. L. Rev. 1059 (2008) Philosophy, Political Morality, and History: Explaining the Enduring Resonance of the Hart-Fuller Debate; Lacey, Nicola