Roman law. Roman law, the law ancient Rome from the time of the founding of the city in 753 BCE until the fall of the Western Empire in the 5th century CE. It remained in use in the Eastern, or Byzantine, Empire until 1453. As a legal system, Roman law has affected the development of law in most of Western civilization as well as in parts of the East. It forms the basis for the law codes of most countries of continental Europe (see civil law) and derivative systems elsewhere. The term Roman law today often refers to more than the laws of Roman society. The legal institutions evolved by the Romans had influence on the laws of other peoples in times long after the disappearance of the Roman Empire and in countries that were never subject to Roman rule. To take the most striking example, in a large part of Germany, until the adoption of a common code for the whole empire in 1900, the Roman law was in force as “subsidiary law”; that is, it was applied unless excluded by contrary local provisions. This law, however, which was in force in parts of Europe long after the fall of the Roman Empire, was not the Roman law in its original form. Although its basis was indeed the Corpus Juris Civilis—the codifying legislation of the emperor Justinian I—this legislation had been interpreted, developed, and adapted to later conditions by generations of jurists from the 11th century onward and had received additions from non-Roman sources.