Henry Farrell ponders different sorts of international law:
[T]he but he did it first’ excuse is not, and cannot be a justification for committing war crimes. Nor does the self-hating Jew’ claim, or other ways of attacking the messenger ... really stick if you are unnecessarily killing or seriously injuring hundreds or thousands of civilians, you are unnecessarily killing or seriously injuring hundreds or thousands of civilians, and there is no very good way of getting around this awkward fact.
Both Gideon [Rachman] and Eric [Posner] would point to the undoubted fact that the leading politicians of great powers (or their important clients) are highly unlikely to find themselves in the dock for war crimes. But direct punitive sanctioning is not the only effect of law. It can influence the perceived legitimacy of a particular state, its actions and its leadership. It is quite clear that Israel has taken a substantial reputational hit from the Goldstone report, even if it will never be condemned by the UN Security Council, and that Israel’s leaders are worried and upset about this.
And that is a good thing (even if it is inconceivable that Hamas' leaders would ever begin to feel something similar).