Library in Verona; and that definition seems to have been approved, as it was adopted, by the compilers of the Institutes of the Emperor Justinian.
“Quod naturalis ratio inter omnes homines constituit, id apud omnes populos peraeque custoditur, voeaturque Jus Gentium, quasi quo jure omnes gentes utuntur; et populus itaque Romanus partim suo proprio, partim communi omnium hominum jure utitur.”—Inst. 1. I. tit. II. § 1.
This formal definition harmonises in substance with the view of Cicero, who contrasts the Jus Gentium, which is common to all mankind as rational beings, with the leges populorum, or those rules of municipal jurisprudence which are special to each state, and which correspond to the Jus Civile of the Institutes. “Neque vero hoc solum naturâ, i.e. jure gentium, sed etiam legibus populorum, quibus in singulis civitatibus respublicae continentur, eodem modo constitutum est, ut non liceat sui commodi causa nocere alicui,”—(Off. 1. III. c. 5.) We must not, however, suppose that the Romans had not at any time any definite notions of international law. The Collegium Fetialium was not a mere heralds’ college. It was the duty of that body to act as ambassadors as well as heralds, to advise the state in negotiations of peace or alliance, and to regulate the general intercourse of Rome with foreign nations. Niebuhr expressly styles them judges of international law; and there can be no doubt that they committed their decisions and forms of proceeding to writing, and thus constituted a written body of Fetial Law. We find Cicero accordingly justifying the formal surrender of Regulus, on the part of the Roman Senate, to the Carthaginians, on the ground that the war with the Carthaginians was a war with a rightful and lawful
