The second ground, as I said, of a righteous war is the self-defense of the prince or of his subjects.  This ground also is matter of both natural and divine right; for even as self-defense is a natural right, on which right is founded the rule of vim vi repellere, so too in the prince is the defense of his subjects—­for the care which the prince has of his subjects is as essential on his part as is the care which each one of them has for himself; hence, if the subjects are aggrieved by their enemies, the prince may justly in their defense make war, and vim vi repellere.  This is much better than that the individual should himself avenge the wrong; for the individual can lawfully defend himself and his property only in continente, as Sylvester declares (Bellum, 2 Sec. 3), but he may not avenge past wrongs, nec sua repetere save by recourse to his judge and superior. [17] Whatever goes beyond that is contrary to law and good government and, as Cajetan says, is extra moderamen tutelae, [18] it being an essential condition of the right vim vi repellere that it be done cum moderamine.  But the prince and the state have the same authority with respect to their enemies at whose hands they have suffered injury, which they have with regard to their own subjects; and hence not only may they defend themselves lest either they or their subjects suffer injury, but they may avenge injuries by inflicting punishment, exact satisfaction for damage done, and take the enemies’ lives, if so the quiet and safety of their subjects require.  Under this head come the many wars waged by King David against the Philistines, mentioned in the Scriptures; as also the war of the Machabee captains against the kings Antiochus and Demetrius.

The third cause and ground is rebellion and disobedience of subjects.  This was the ground of David’s war with Sheba, son of Bichri, who raised a revolt, as you may read in II Sam. 20; [19] and this is what St. Augustine says (Contra Faustum Manichaeum, I. 22, c. 74):  Adversus violentiam resistentium sive deo sive aliquo legitimo imperio jubente gerenda ipsa bella suscipiuntur a bonis ubi eos vel jubere tale aliquid vel in talibus obedire juste ordo ipse constringit (in c. Quid culpatur, ubi supra.) [20]