Legal Principles, Discretion and Legal Positivism: Does Dworkin's Criticism on Hart also Apply to Kelsen?

This essay investigates the relation between a positivist (supposed) model of rules and discretion, and, therefore, between legal principles, discretion and legal positivism. First it intends to show that Hart's and even Kelsen's positivist models were not models of rules in Dworkin's sense, and that, even if they were, conceiving law as a model of rules would not be the main cause that would lead someone to defend discretion. Then it is claimed that the reason why Hart and Kelsen defended discretion was that they did not develop elaborated theories of legal adjudication and that the reason why discretion should be fought depends on how one conceives the relation between law and moral.