Legal philosophers, especially of the positivist variety, traditionally have assumed that the proponents of natural law theory present too facile an answer to the vexed question of whether an unjust law can be said to exist when it is duly sanctioned by legal and political authority. If not disappointed by the answer itself, they have been most unhappy with the explanation that accompanies it and, indeed, are prepared to challenge the very foundations of a theory of law which pays so little heed—either empirically or in terms of pure logic—to the actual operations of existing legal systems. Kant initiated the rebellion against the law–morality equation by distinguishing them as two separate spheres of activity.) Subsequent philosophers, thanks to the analogy between legal rules and the rules of a game, inaugurated the movement towards the purely systemic analysis of law.
Thomas E. Carbonneau, The Implicit Teaching of Utopian Speculations: Rousseau's Contribution to the Natural Law Tradition, 3 SEATTLE U. L. REV. 123 (1979).