Catechism of the Catholic Church §1909 — excerpt
Finally, the common good requires peace, that is, the stability and security of a just order. It presupposes that authority should ensure by morally acceptable means the security of society and its members.
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.