The Nuremberg principles were a set of guidelines for determining what constitutes a war crime. The document was created by the International Law Commission of the United Nations to codify the legal principles underlying the Nuremberg Trials of Naziparty members following World War II. (Wiki)
Main article: Superior Orders
Principle IV states: "The fact that a person acted pursuant to order of his Government or of a superior does not relieve him from responsibility under international law, provided a moral choice was in fact possible to him".
This principle could be paraphrased as follows: "It is not an acceptable excuse to say 'I was just following my superior's orders'".
Previous to the time of the Nuremberg Trials, this excuse was known in common parlance as "Superior Orders". After the prominent, high profile event of the Nuremberg Trials, that excuse is now referred to by many as "Nuremberg Defense". In recent times, a third term, "lawful orders" has become common parlance for some people. All three terms are in use today, and they all have slightly different nuances of meaning, depending on the context in which they are used.
The Nuremberg Principles are used by the winners to condemn the losers. They are certainly NEVER applied by a regime in dealing with its own people. The regime defines who are heroes and who are traitors, not "the people" and in most cases either the people support the regime or are coerced into doing so. Hence the fact that Bradley Manning is not allowed to use Principle IV in his defence (or the First Amendment or practically anything else from what I can gather). Julian Assange and Edward Snowden will spend their lives in hiding or in prison. History may consider them heroes but the American Empire never will.