On the acquisition of things taken in war

Besides the impunity among men in relation to certain actions, which we have discussed up to this point, there is also another effect characteristic of public war according to the law of nations (iure gentium proprius). According to the law of nature, by a lawful war we acquire things which are either equal to that which, although it was owed to us, we could not otherwise obtain; or we inflict upon the guilty a loss that does not exceed an equitable measure of punishment, as has been said elsewhere.

What the [volitional] law of nations is on this subject

By the [volitional] law of nations, not merely he who wages war for a just cause, but in a public war also, anyone at all becomes owner, without limit or restriction, of what he has taken from the enemy. That is true in this sense, at any rate, that both the possessor of such booty, and those who hold their title from him, are to be protected in their possession by all nations; and such a condition one may call ownership so far as its external effects are concerned.

On the authority of Aristotle also we read: ‘The law is a sort of agreement, according to which things taken in war belong to those who take them.’ … ‘What is taken from the enemy, by the law of nations becomes at once the property of those who take it’, says [Justinian].… Aristotle said ‘acquisition by war is a method according to nature’.