The Corpus forms the basis of Latin jurisprudence (including ecclesiastical Canon Law) and, for historians, provides a valuable insight into the concerns and activities of the later Roman Empire. As a collection, it gathers together the many sources in which the laws and the other rules were expressed or published (proper laws, senatorial consults, imperial decrees, case law, and jurists’ opinions and interpretations). It formed the basis of later Byzantine law, as expressed in the Basilika of Basil I and Leo VI the Wise. The only western province where the Justinian Code was introduced was Italy, from where it was to pass to western Europe in the 12th century, and become the basis of much European law code. It eventually passed to eastern Europe, where it appeared in Slavic editions, and it also passed on to Russia.
It was not in general use during the Early Middle Ages. After the Early Middle Ages, interest in it revived. It was “received” or imitated as private law, and its public law content was quarried for arguments by both secular and ecclesiastical authorities. The revived Roman law, in turn, became the foundation of law in all civil law jurisdictions. The provisions of the Corpus Juris Civilis also influenced the canon law of the Roman Catholic Church; it was said that ecclesia vivit lege romana—the church lives by Roman law. Its influence on common law legal systems has been much smaller, although some basic concepts from the Corpus have survived through Norman law—such as the contrast, especially in the Institutes, between “law” (statute) and custom. The Corpus continues to have a major influence on public international law. Its four parts thus constitute the foundation documents of the western legal tradition.
