Catechism of the Catholic Church §1956 — excerpt
The natural law, present in the heart of each man and established by reason, is universal in its precepts and its authority extends to all men.
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.
Also cites: Cicero, Rep. III, 22, 33