It was the system of law used by the Romans from the eighth century B.C. until the fall of the empire (Rome, in the West Roman Empire, was toppled in A.D. 476; the East Empire fell in A.D. 1453). Justinian the Great (483–565), the emperor of the East Roman Empire, is credited with codifying (writing and organizing) Roman law by ordering the collection of all imperial statutes and of all the writings of the Roman jurists (judges and other legal experts). Justinian appointed the best legal minds in the empire to assemble, write, publish, and update the code; work began in and continued until the time of Justinian’s death, in 565. The result was the Corpus juris civilis (Body of Civil Law), also called the Justinian Code. It consists of four parts: the Codex (a collection of imperial statutes), the Digest (the writings and interpretations of Roman jurists), the Institutes (a textbook for students), and the Novels (the laws enacted after the publication of the Codex).

Though largely suspended during the Middle Ages (500–1350), it was kept alive in the canon law of the medieval church and was handed down through the centuries. It forms the basis of modern civil law in most of continental Europe and in other non-English-speaking countries, as well as in the state of Louisiana. Nations or states whose systems of justice are based on civil law rely not on precedents set by the courts (which is the common law system of the United States and Great Britain), but rather on the letter of the law—the statutes themselves.