High Quality Content by WIKIPEDIA articles! Ius gentium, Latin for "law of nations", was originally the part of Roman law that the Roman Empire applied to its dealings with foreigners, especially provincial subjects. In later times the Latin term came to refer to the natural or common law among nations considered as states within a larger human society, especially governing the rules of peace and war, national boundaries, diplomatic exchanges, and extradition, that together with jus inter gentes makes up public international law.