Catechism of the Catholic Church §2455 — excerpt
The moral law forbids acts which, for commercial or totalitarian purposes, lead to the enslavement of human beings, or to their being bought, sold or exchanged like merchandise.
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.