Robert Alexy defines law as including a claim to moral correctness and demonstrating social efficacy. This paper argues that law's social efficacy is not merely an observable fact but is undergirded by moral commitments by rulers that it is possible for their subjects to follow the rules, that the rulers and others will also follow the rules, that subjects will be protected from violence if they act in accordance with the rules, and that subjects will be entitled to legal redress (...) if others act violently towards them otherwise than in accordance with the rules. Alexy is correct in his conclusion that a system of norms that is not by and large socially efficacious is not a valid legal system, but wrong insofar as he follows legal positivism in distinguishing this aspect of law's validity from law's claim to moral correctness. (shrink)