CCC 2263

The legitimate defense of persons and societies is not an exception to the prohibition against the murder of the innocent that constitutes intentional killing. "The act of self-defense can have a double effect: the preservation of one's own life; and the killing of the aggressor.... the one is intended, the other is not."⁶⁵ St. Thomas Aquinas, STh II-II, 64, 7, corp. art.