The emperor believed that law was as essential to the security of the empire as military power. His legal achievement (like his martial effort) was an attempt to ensure the power and legacy of his reign.
Justinian selected and changed a commission, which included Tribonian, the day’s greatest legal mind, with the task of organizing the past and present laws of the empire.
In 529 the commission completed its work, the Code, which arranged centuries of imperial legislation, removing that which was no longer needed. This code was revised and updated in 534. Copies were distributed throughout the empire, and only laws that were recorded in it were valid in the empire’s courts.
After this Justinian entrusted Tribonian and his commission with the task of compiling, editing, and organizing past legal decisions or commentaries on the laws. This work, known as the Digest, was completed in 533. It was divided into 50 books, by subject headings for easy reference.
Justinian further entrusted Tribonian with the publication (534) of an official legal textbook, the Institutes, for the training of lawyers. These three parts—along with a fourth part consisting of Justinian’s new laws called Novels (meaning new laws)—all written in Latin, became known as the Corpus Juris Civilis, or Body of Civil Law.
This work had a profound effect on future legal procedure. The Corpus influenced Byzantine law down to 1453, when the Byzantine Empire fell to the Ottoman Turks. The Corpus largely influenced Byzantium through a later Greek legal compilation known as the Basilika (ninth century).
In the West, Roman law was diminished by the transition to Germanic rule during the early Middle Ages. In the 11th century, however, legal scholars at the University of Bologna in Italy revived the study of Justinian’s Corpus.
In the 12th century this study led Gratian, a Bolognese monk, to create a systematic organization of canon law (church laws) called the Decretum. This study also gave birth to secular legal developments in western Europe. The Code of Justinian still heavily influences many European legal systems.