The Byzantine Emperor who is famous for codifying Roman law is Justinian I. He reigned from 527 to 565 and during his reign, he commissioned a team of lawyers to collect and revise the laws of the Roman Empire. The result was the creation of the Codex Justinianus, a collection of Roman laws that served as the basis of Byzantine law and influenced legal systems throughout Europe. Justinian's codification of Roman law played a significant role in the preservation and development of Roman legal tradition and helped to lay the foundations for the modern Western legal system.