Byzantine Law was essentially a continuation of Roman Law with Christian influence, however, this is not to doubt its later influence on the western practice of jurisprudence. Byzantine Law was effectively devolved into two spheres, Ecclesiastical Law and Secular Law.
Influences and sources 
Byzantium inherited its main political, cultural and social institutions from Rome. Similarly, Roman law constituted the basis for the Byzantine legal system. For many centuries, the two great codifications of Roman law, carried out by Theodosius II and Justinian respectively, were the cornerstones of Byzantine legislation. Of course, over the years these Roman codes were adjusted to the current circumstances, and then replaced by new codifications, written in Greek. However, the influence of Roman law persisted, and it is obvious in codifications, such as Basilika, which was based on Corpus Juris Civilis. In the 11th century, Michael Psellos prides himself for being acquainted with the Roman legal legacy ("Ἰταλὥν σοφία").
In accordance with the late Roman legal tradition, the main source of law (fons legum) in Byzantium remained the enactments of the emperors. The latter initiated some major codifications of the Roman law, but they also issued their own "new laws", the Novels ("Novellae", "Νεαραὶ"). In early Byzantine (late Roman) era the legislative interest of the emperors intensified, and laws were now regulating the main aspects of public, private, economic and social life. For example, Constantine I was the first to regulate divorce and Theodosius I intervened in faith issues, imposing a specific version of the Creed. From Diocletian to Theodosius I, namely during approximately 100 years, more than 2,000 laws were issued. Justinian alone promulgated approximately 600 laws. Gradually, the legislative enthusiasm receded, but still some of the laws of later emperors, such as Leo III's Novels, are of particular importance. Custom continued to play a limited role as a secondary source of law, but written legislation had a precedence.
Early Byzantine Period 
Codex Theodosianus 
Corpus Iuris Civilis 
Soon after his accession in 518, Justinian appointed a commission to collect and codify existing Roman law. A second commission, headed by the jurist Tribonian, was appointed in 530 to select matter of permanent value from the works of the jurists, to edit it and to arrange it into 50 books. In 533 this commission produced the Digesta.
Although Law as practiced in Rome had grown up as a type of case law, this was not the "Roman Law" known to the Medieval, or modern world. Now Roman law claims to be based on abstract principles of justice that were made into actual rules of law by legislative authority of the emperor or the Roman people. These ideas were transmitted to the Middle Ages in the great codification of Roman law carried throughout by the emperor Justinian. The Corpus Iuris Civilis was issued in Latin in three parts: the Institutes, the Digest (Pandects), and the Code (Codex). Three of the world's most widespread legal systems are: the common law of the Anglo-American legal tradition, Sharia, and Roman law (in, for instance, most of Europe, Scotland, Quebec and Louisiana).
Middle Byzantine Period 
Following Justinian's reign the Empire entered a period of decline partially enabling the Arab conquests which would further weaken the Empire. These developments contributed to a dramatic weakening of legal standards in the Empire and a substantial drop in the standards of legal scholarship. Legal practice would become much more pragmatic and, as knowledge of Latin in the Empire waned, direct use of Justinian's "Corpus Juris Civilis" would be abandoned in favor of summaries, commentaries, and new compilations written in Greek.
The changes in the internal life of the empire which occurred in the years following the publication of Justinian's code called for a review of the legislation, so as for the requirements of the times should be met. Within the framework of the reforms Leo III the Isaurian, (the first Isaurian emperor), introduced, he provided also for the modification of current laws. In 726 he issued the "Ecloga", that bore his name as well as the name of his son Constantine. "Ecloga", referring to both the civil and criminal law, constituted, as was declared in the title a "rectification (of the Justinian legislation) towards a more philanthropic version". The membership of the editing committee is not known, but its primary mission, however, was, on the one hand, to modify those dispositions not in step with the times and, on the other, to provide judges with a concise legal handbook to help them dispense justice properly.
The dispositions of "Ecloga", influenced by the Christian spirit, as well as by the common law, protected and supported the institution of marriage, increased the rights of wives and legal children, and introduced the equality of all citizens before the law. The penalties of amputation and blindness, not in step, of course, with the Christian character of the enactment, were introduced, most likely, due to the customs of the East, reflecting the Byzantine concept in this period of changes. By means of his "Ecloga" Leo addressed the judges also, inviting them "neither the poor to despise nor the ones unjust to let uncontrolled". Besides, in his effort to deter bribery in the execution of their duties he made their payment local and payable by the imperial treasury. "Ecloga" constituted the basic handbook of justice dispensation up to the days of the Macedonian emperors, that also assumed legislative activity, whereas later it influenced the ecclesiastic law of the Russian Orthodox Church. Formerly the researchers attributed the juridical collections "Farmer's Law", "Rhodian Sea Law" and "Military Laws" to Leo III the Isaurian. These views, however, are no longer valid.
The Farmer's Laws 
With the exception of a few cities, and especially Constantinople, where other types of urban economic activities were also developed, Byzantine society remained at its heart agricultural. An important source regarding law, which reflects in a particularly characteristic way the internal life of the Byzantine villages during the Middle Byzantine Era (7th - end of 12th century) is the "Farmer's Law". Due to its importance, the "Farmer's Law" roused the interest of researchers from a very early stage. Ever since it has been one of the most discussed texts concerning the internal history of Byzantium.
It is a private collection, continuously enriched, and refers to specific cases relevant to rural property within the framework of the Byzantine rural "community". As evident by the dispositions of the "Law", peasants were organized in "communities" and collectively responsible for the payment of the total tax the "community" was liable for, being obliged to pay as well the amounts corresponding to indebted members of the community. As for the chronology of its writing, since the text itself bears no specific date, it is placed somewhere in between the second half of the 6th century and the middle of the 14th. Very early on, it was acknowledged as a legal handbook of great importance and greatly influenced much of the law of the Slavic countries and especially Serbia, Bulgaria and Russia.
The Sea Laws 
Dating problems, similar to the ones of the "Farmer's Law", presents a code of equal character, the "Rhodian Sea Law" (Nomos Rhodion Nautikos). Written probably between 600 and 800, it is a collection of maritime law regulations divided into three parts. The first part refers to the ratification of the "Naval Law" by the Roman emperors. The second specifies the participation of the crew in maritime profits and the regulations valid on the ship, while the third and largest refers to maritime law, as for example to the apportionment of responsibility in case of theft or damage to the cargo or the ship. The "Naval Law" was included in the Basilika of Leo VI the Wise as a complement to book 53.
Ecclesiastical law 
In accordance with the model of the secular legal associations, the canons of the ecclesiastic councils concerned ecclesiastic issues and regulated the conduct of the clergy, as well as of the secular as concerned matters of belief. The "In Trullo" or "Fifth-Sixth Council", known for its canons, was convened in the years of Justinian II (691-692) and occupied itself exclusively with matters of discipline. The aim of the synod was to cover the gaps left in canon law by the previous Fifth (553)and Sixth Ecumenical Councils.
This collection of canons was divided into four parts:
a) The canons ratifying the doctrinal decisions of the first six ecumenical councils along with the teachings of the Fathers of the Church.
b) The canons specifying the obligations of the ministrational clergy.
c) The canons referring to the monks.
d) The canons referring to the secular. The influence of these canons carried on in the future and they were extensively annotated by Balsamon, Zonaras and Aristenos, the three great ecclesiastic jurists of the 12th century.
Later Byzantine law 
The following legal texts were prepared in the later Byzantine Empire:
- The Prochiron of Basil the Macedonian, c. 870 or 872, which invalidates parts of the Ecloga and restores Justinians Laws, as well as Hellenising arcane Latin expressions.
- The Epanagoge (repetita proelectio legis), also of Basil the Macedonian, together with his sons, a second edition of the Prochiron, c.879 - 886
- The Eisagoge of Photios, which includes novel law, c.880
- The Basilicae (repurgatio veterum legum) or Basilics of Leo the Philosopher, together with his brother Alexander and Constantine VII, c.900 or 906-11, which attempts to synthesise 6th century commentaries and glosses on Justinians laws by headings, and remove contradictions. By the 11th century, the Basilics had replaced Justinian's laws as the primary source of Roman law. An abridged version, the Synopsis Basilicorum, was also prepared in the 10th century.
- The Epitome Legum, later known as the Epitome ad Prochiron mutata, a synthesis of Justinian and the Epanagoge, c. 920-1
- The Epanagoge aucta, a revision of the 9th century Epanagogue from c.11th century.
- The Prochiron aucta, a revision of the 9th century Prochiron from c.13th century.
Other jurists (including at least one Emperor) prepared private collections of cases and commentaries, but these did not form the body of law used by jurists at large. It is held that the 113 Novels of Leo the Wise fall into this category.
Lokin argues that while later legal texts tended to rearrange or explain the 6th century work of Justinian, rather than create new law, they did alter the locus of authority for law (legis vigor) from the Emperor to God. In Justinian's work, Mosaïc Law and God's authority support the Emperor, and are consultative, but do not temper his absolute authority. This process has already begun in the Ecloga, which states law is God-given by way of Isiah 8:20, and is made explicit first in the Prochiron. There was, however, 'legislative creep' over this period, where the redaction of old laws and case law created new laws in effect, although not explicitly cited as such.
See also 
- A. Cameron, The Byzantines, p. 153; G. Mousourakis, Context of Roman Law, p. 397.
- M.T. Fögen, "Legislation in Byzantium", pp. 53–54; R. Morris, "Dispute Settlement", 126; G. Mousourakis, Context of Roman Law, pp. 399–400.
- M.T. Fögen, "Legislation in Byzantium", pp. 56, 59.
- A. Cameron, The Byzantines, p. 153; M.T. Fögen, "Legislation in Byzantium", pp. 53–54.
- R. Morris, "Dispute Settlement", 126; G. Mousourakis, Context of Roman Law, pp. 401–402.
- Mousourakis, George. The Historical and Institutional Context of Roman Law. pp. 402–403. ISBN 0-7546-2108-1.
- Lambert Mears, Analysis of M. Ortolan's Institutes of Justinian, pp64-66
- Laiou and Simon (eds), Law and Society in Byzantium: Ninth-twelfth Centuries, p.71
- Laiou and Simon (eds), Law and Society in Byzantium: Ninth-twelfth Centuries, p.77
- Laiou and Simon (eds), Law and Society in Byzantium: Ninth-twelfth Centuries, p.85
- Cameron, Averil (2009). The Byzantines (in Greek [translated from the original by Giorgos Tzimas]). Athens: Editions Psychogios. ISBN 978-960-453-529-3.
- Fögen, Marie Theres (1994). "Legislation in Byzantium: A Political and a Bureaucratic Technique". In Laiou, Angeliki E.. Law and Society in Byzantium. Dumbarton Oaks. ISBN 0-88402-222-6.
- Morris, Rosemary (1992). "Dispute Settlement in the Byzantine Provinces in the Tenth Century". In Davies, Wendy; Fouracre, Paul. The Settlement of Disputes in Early Medieval Europe. Cambridge University Press. ISBN 0-521-42895-5.
- Mousourakis, George (2003). The Historical and Institutional Context of Roman Law. Ashgate Publishing. ISBN 0-7546-2108-1.