Digestorum libri
Ex libro LXXXIV
Julianus, Digest, Book XCIV. In cases where there are no written laws, that should be observed which has been established by usage and custom, and if anything is lacking therein, then whatever is nearest to, and resulting from it should be observed; and if even this does not exist, then the law which is used by the City of Rome must be followed. 1An ancient custom is not improperly observed as a law (and this is what is called law established by usage). For as the laws themselves restrain us for no other reason than because they are accepted by the judgment of the people—for it is but proper that what the people have approved without being written should bind all persons—for what difference does it make whether the people have manifested their will by vote, or by acts and deeds? Wherefore the rule has also been most justly adopted that laws shall be abrogated not only by the vote of the legislator, but also through disuse by the silent consent of all.