So a Question is:

How do we judge the grounds for rights if there are no first principles to guide that search. Is what's right, what's a right, merely a contingent historical judgment grounded on nothing but consensus about the meaning of experience? If no there are no standards to guide these judgments, the consequence for the meaning of rights, moral and legal, is sheer relativism without a basis for preferring one sovereign consensus over another at any given time. But if there are first principles--the value of life, equality, the rule of law, for example--where do they come from? It strikes me that Dershowitz erases the very ground his argument stands on--judging wrongs and deriving rights from them--by denying the existence of the very principles he wants recourse to as standards for making judgments about wrongs.