The idea of justice according to law is exemplified by common law thought, in which principle and precedent are interlocked and interdependent. The law is constituted neither by its socially authoritative sources, regarded as social fact, nor by moral judgment about their effects. It is a moral construction of legal practice, interpreting its various rules and arrangements as parts of an integrated scheme of justice. Justice is sought by adherence to practice, understood in the light of the ideals it embodies on correct analysis. Legal obligations are moral obligations and legal reasoning is moral reasoning, but in each case context is critical. The requirements of justice are discerned, in large part, by exploration of the legal tradition in which particular issues arise for decision. It is an internal, interpretative inquiry, drawing on the moral resources of that tradition. Conflict between political ideals must be resolved internally as part of that inquiry; we are obligated to obey the law as correctly determined. These points are reinforced by critique of work by Dworkin, Greenberg, Hershovitz, and Waldron.
Allan, TRS, Principle, Practice, and Precedent: Vindicating Justice, According to Law (October 1, 2017). University of Cambridge Faculty of Law Research Paper No 48/2017.