Catechism of the Catholic Church §2414 — excerpt
The seventh commandment forbids acts or enterprises that for any reason - selfish or ideological, commercial, or totalitarian - lead to the enslavement of human beings, to their being bought, sold and exchanged like merchandise, in disregard for their personal dignity.
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.
Whole chapters cited: Philemon 16