The normativity of law must be founded on autonomous reasoning. Hence, a crucial issue of a theory of law as a normative system is the relevance of moral argument for legal validity. No specific interpretation of morality is implied here. Moral validity is understood as normativity in the sense that the validity of a norm implies a requirement that it be applied and followed. Hence, the issue is how this requirement can be justified regarding law in the model of autonomous reasoning. In this approach, a conceptually necessary connection between law and morality follows because legal validity implies an obligation to apply and follow it, at least for law-applying organs. It is a demand of practical rationality that a justification is presented for such a normative claim. Hence, legal validity requires a moral justification.