Catechism of the Catholic Church §2313 — excerpt
Non-combatants, wounded soldiers, and prisoners must be respected and treated humanely. Actions deliberately contrary to the law of nations and to its universal principles are crimes, as are the orders that command such actions.
This translation is under copyright, so only the cited words are quoted here. Follow the link for the full text. Translation: English translation of the Catechism of the Catholic Church, 2nd ed. (Libreria Editrice Vaticana), as posted at vatican.va.