"The precepts of the law are these: to live honestly, to injure no one, and to give every man his due. The study of law consists of two branches, law public and law private. The former relates to the welfare of the Roman State; the latter to the advantage of the individual citizen. Of private law then we may say that it is of threefold origin, being collected from the precepts of nature, from those of the law of nations, or from those of the civil law of Rome." Source: From The Institutes of Justinian, B. Moyle, trans.3rd ed. (Oxford: Oxford University Press, 1896), pp. 3-5.

This excerpt from the Justinian Code shows how the Byzantine Empire

preserved Greco-Roman culture
reformed the Roman Catholic Church
split from Western Roman legal traditions
established an Eastern Orthodox Church separate from Rome