Catechism of the Catholic Church §1976 — excerpt
"Law is an ordinance of reason for the common good, promulgated by the one who is in charge of the community" (St. Thomas Aquinas, STh I-II, 90, 4).
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.