Law as a normative systems requires justification through autonomous reasoning. There seems to be no other way to ground the normative claim of law. Normative validity implies that a norm ought to be recognised, applied, and followed by its addressees. Legal norms, claiming normative validity, hence imply an obligation at least of the law-applying organs to recognise, apply and follow these norms. This obligation can hold only if there is a justification for it, and this justification must be founded on autonomous morality. That is, one must show that every autonomous agent must accept as correct the claim that the respective norm is valid. The normative validity of law hence depends on autonomous morality. However, law is not identical with morality. It is defined also by its authoritative character. The interplay of authoritative character and autonomous justification manifests in three dimensions of law: law as a system of positive norms, as a normative system, and as a practice.