There are seven Nuremberg Principles. Every person working for the government of the USA has an obligation under international law to report any act committed by the government which violates the Nuremberg Principles. There can be no doubt that Snowden acted in accordance to international law. (The same is true of Bradley Manning, BTW.) Many actions taken by the government of the USA in recent years are in clear violation of the Nuremberg Principles. Supposed legal analyst Jeffrey Toobin presents a weak argument to the contrary, but is basically put in his place by Wikileaks spokesman Kristinn Hrafnsson.
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'".
LINK: http://en.wikipedia.org/wiki/Nuremberg_principles
NOTE: I decided to post this topic to Technology and Gadgets since technology is a huge part of this story. Not only are Snowden and Manning often referred to as hackers, but Wikileaks is involved and all the leaks of classified information involved the use of technology. On top of that, many of the violations of human rights revealed through the leaks involve the use of technology.