A famous Byzantine emperor was Justinian I. Justinian reigned from 527 to 565 AD. Justinian created a set of laws called the Justinian Codex. This code said that the emperor made all the laws and also interpreted the laws. The Justinian Code had the force of law throughout the empire. Many of our modern laws date back to the Code of Justinian. The most famous center for legal doctrine in the Byzantine Empire was the Faculty of Law in Constantinople. It was founded in 425, closed in 717 when Constantinople was besieged by the Umayyads, and only reopened in 866. It probably remained open until the sack of Constantinople by the crusaders in 1204.  All these books were later compiled by the Athonite monk Nicodemus the Hagiorite and became the basis of modern Eastern Orthodox canon law, its pedalion.
In Western Europe, the influence of Roman/Byzantine law became more indirect after the fall of the Roman Empire, although it was still significant throughout much of the Middle Ages. During the European Renaissance, Western scholars adopted the Codex of Justinian as the basis for jurisprudence, avoiding many later legal developments of the Byzantine Empire, such as the Ekloga. This was greatly influenced by the East-West divide (Roman Catholic versus Eastern Orthodox) in the Church. The perception in the West was that Roman law recorded in Latin was truly Roman, while later laws written in Greek were different and foreign. After the Islamic conquests of the eastern Mediterranean, Islamic caliphates gradually codified their legal systems with Romano-Byzantine law as an important model. Indeed, it has been suggested that it was the publication of the Ecloga that stimulated the first major codification of Islamic imperial law.  The laws created by Justinian and his experts lasted in one form or another nearly a millennium until the fall of the Byzantine Empire in 1453 AD. New Byzantine laws, of course, were added over the centuries as each emperor issued his own edicts and society grew. Leo VI (r.
886-912 AD), for example, produced another collection of Byzantine edicts and had everything translated into Greek, since almost no one understood Latin anymore (few ordinary people would have done so even in the time of Justinian). In the west, the Codex of Justinian was largely lost or never present in many places due to the limited western extent of Byzantine territories. The Latin version known today has been painstakingly restored over many centuries. The only known manuscript that once contained the entire Latin codex is a Veronese palimpsest from the 6th or 7th century; They are now only fragments.   In his homeland of the Byzantine Empire, the code was translated into Greek, which had become the language of government, and adapted into a basilica in the 9th century. It seems that the Latin code was shortened to a “Codex Epitome” in the Middle Ages, omitting inscriptions and making many other changes.  In the 8th or 9th century, the last three books of the codex were separated from the others, and many other laws of the first nine books, including all in Greek, were abandoned.  Essentially complete versions of the Justinian Codex were published towards the end of the 12th century.
It was restored in the nineteenth century, and the humanists of the 16th century added the laws originally promulgated in Greek.  Paul Krüger created the modern standard version of the codex in 1877.  Lokin argues that while later legal texts tended to reorganize or explain Justinian`s work from the 6th century onwards rather than create a new law, they changed the place of authority for the law (legis vigor) from Caesar to God. In Justinian`s work, the Mosaic law and God`s authority sustain Caesar and are consultative, but do not diminish his absolute authority. This process has already begun in the Ekloga, which states that the Law is given by God through Isaiah 8:20, and is first made explicit in the Prochiron.  During this period, however, there was a “legislative shift,” in which new laws came into force through the drafting of old laws and case law, but which were not explicitly designated as such.  Although law, as practiced in Rome, developed as a kind of jurisprudence, it was not the “Roman law” known to the medieval or modern world. Now Roman law claims to be based on abstract principles of justice, transformed into actual legal norms by the legislative power of the emperor or the Roman people.
These ideas were transferred to the Middle Ages in the great codification of Roman law, which was carried out throughout by Emperor Justinian. The Corpus Iuris Civilis was published in Latin in three parts: the Institutes, the Collections (Pandects) and the Codex (Codex). It was the last major legal document written in Latin. The Justinian Codex (Latin: Codex Justinianus, Justinianeus or Justiniani) is part of the Corpus Juris Civilis, the codification of Roman law ordered in the early 6th century AD by Justinian I, the Eastern Roman Emperor in Constantinople. Two other entities, the Digests and the Institutes, were created during his reign. The fourth part, the Novellae Constitutiones (New Constitutions or Romans), was compiled unofficially after his death, but is now also considered part of the Corpus Juris Civilis. Shortly after Justinian became emperor in 527, he decided that the empire`s legal system needed to be repaired. There were three codices of imperial laws and other individual laws, many of which were contradictory or obsolete. The Codex Gregorianus and the Codex Hermogenianus were unofficial compilations. (The term “codex” refers to the physical appearance of works that are in book form rather than papyrus scrolls. The transition to the codex took place around 300 AD.)  The Codex Theodosianus was an official collection commissioned by Theodosius II.  In February 528, Justinian promulgated the Constitutio Hac quae necessario, which created a ten-member commission to examine these earlier compilations as well as individual laws, to eliminate anything unnecessary or obsolete, to make any changes it deemed appropriate, and to create a single compilation of existing imperial laws.  The commission was headed by the Praetorian Prefect John the Cappadocian and included Tribonian, who would later direct the other projects of the Corpus Juris Civilis.
 The war effort to reconquer the western part of the empire forced Justinian to raise taxes on the population of the Byzantine Empire. Roman citizens were angry with Justinian over the high taxes on the war effort, and he became unpopular. Even more unpopular was Empress Theodora, Justinian`s wife, because she was originally a circus performer and came from the lower class of Romans. “Who was this woman who had such control over her husband`s decisions?” they thought. Theodora did not lag behind her husband, but proposed laws that protected women`s rights in the empire. Although the Code of Justinian is not a new legal code per se, it has rationalized hundreds of years of existing Roman laws. Contradictions and conflicts have been eliminated and all existing laws not contained therein have been repealed.