At the end of World War II in 1945, judges were appointed from the United States, Great Britain, the Soviet Union, and France to form an international court of judges to bring to trial Nazi leaders accused of committing war crimes, crimes against world peace, and crimes against humanity. The evidence that was presented was in the form of films and photographs of the victims of the atrocities.
The United States government under President Harry S. Truman appointed Assistant Justice Robert H. Jackson to function as Chief Prosecutor at the trails held in Nuremberg. Justice Jackson also participated in establishing an International Military Tribunal to try the individuals accused of these crimes. The 24 Nazi leaders were indicted on October 18, 1945.
In defending themselves, the officers insisted that whatever they did was in obedience to the commands and laws of their government. Their defense was founded on the model of positive law, which posits that the only binding laws for humanity are the laws that are enacted by human governments; laws that reflect and address the needs of the citizenry. Positive law is different from the Moral Law of God which is universal and transcends laws of human governments. According to positive law, some actions may be deemed legal although they might be perceived to be morally wrong. The German defendants insisted that they had done no wrong since they were merely obeying laws that resonated with their constitution or political ideological manifesto, Mein Kampf, at the time. What they did, they said, was for the good of the German people, according to their law then. As such, they had acted in a legal manner. Of course, their laws were a reflection of Darwin’s theory of macroevolution and survival of the fittest, which advocates that individuals whose phenotype adapts most to the environment are the ones more likely to survive the rigors of nature. According to positive law, a sovereign nation does not have to answer to other countries’ legal standards.
Without appealing to a standard of justice that is outside of our world, Justice Jackson and his associates seemed to have no case against the German officers; as far as positive law was concerned. But Jackson was wise enough to appeal “to objective and universal natural law with respect to personal moral accountability. This appeal not only linked morality to law but also placed morality prior to human legislation…Jackson was arguing for the existence of higher moral laws that transcend governments.” [1]
The International community was outraged by what had happened in Nazi Germany because it was morally wrong although the German government at the time thought it was legal under their constitution. As such, it was necessary for the tribunal to convict the individuals who had committed heinous acts against innocent human beings and punish them.
Similarly, people such as William Wilberforce and scores of others fought the scourge of slavery because it was morally repugnant although some governments had legalized it. Other moral violations such as ethnic cleansing have been met with international outrage wherever they have surfaced because they were morally reprehensible, even if they might have been legalized by functioning governments at the time.
Therefore, we can conclude that the Moral Law continues to be transcendent over positive law, and is still written on our hearts. That is why we object to unconscionable activities against other people, because we all have intrinsic value-we bear the Imago Dei.

Source
[1] Norman Geisler & Peter Bocchino (2001). Unshakable Foundations: Contemporary Answers to Crucial Questions about the Christian Faith. Bethany House Publishers. Bloomington, Minnesota. pp. 222