Once Justinian had secured his throne as emperor of the Byzantine Empire in 527, he turned his attention to the reformation of domestic matters. The principal among these was the codification of the various laws on which the empire's system of justice was built. Roman law, as these laws were generically called, had existed in many forms for many centuries. Emperors and senates had issued legal directions since the earliest days of late antiquity, few of which had been systematically published or catalogued. In addition, judicial opinions had been issued frequently on these laws, many of which were contradictory and inaccessible. When legal collections were attempted—for example, two in the third and fourth centuries—their usefulness was disputed. Finally, earlier imperial attempts at correcting the situation, primarily by Valentinian III in the west and Theodosius II in...