Claiming that the organization was breaking the laws, and so he was legally protected in leaking information–that would be roughly a whistleblower defense–is an affirmative defense. It’s similar to saying that I was legally justified in shooting someone because they were assaulting me. But affirmative defenses require you to show up in court, not defect to a hostile country that is doing far, far worse than the US has done in the last century or so.
If he truly believed that what he was doing was legally defensible, then he would have stayed and lawyered up.