[ULPIANUS libro primo institutionum. ] §49.15.24.prHostes sunt, quibus bellum publice populus Romanus decreuit uel ipsi populo Romano: ceteri latrunculi uel praedones appellantur.
[ULPIAN, Book 1 of Institutes] are those against whom the Roman people have publicly declared war, or who themselves have declared war against the Roman people; the others are called bandits or robbers.
et ideo qui a latronibus captus est, seruus latronum non est, nec postliminium illi necessarium est: ab hostibus autem captus, ut puta a Germanis et Parthis, et seruus est hostium et postliminio statum pristinum recuperat.
And therefore, he who has been captured by robbers is not a slave of the robbers, nor is postliminium necessary for him; but he who has been captured by enemies, as for example by the Germans or the Parthians, is both a slave of the enemies and recovers his former status by postliminium.