A public war according to the law of nations

In a previous passage, we began to say that, by authors of repute, a war is often called lawful not from the cause from which it arises, nor, as is done in other cases, from the importance of its exploits, but because of certain peculiar legal consequences. Of what sort a lawful war is, however, will best be perceived from the definition of enemies given by the Roman jurists. ‘Enemies are those who in the name of the state declare war, upon us, or upon whom we in the name of the state declare war; others are brigands and robbers’, says Pomponius.

It needs only to be noted further that we may understand that anyone who has the supreme authority in a state may take the place of the Roman people in our illustration. ‘An enemy’, says Cicero, ‘is the one that has a state, a senate, a treasury, the agreement and concord of the citizens, and the power, if the course of events leads thereto, to conclude peace and an alliance’.