Catechism of the Catholic Church §1868 — excerpt
Sin is a personal act. Moreover, we have a responsibility for the sins committed by others when we cooperate in them: - by participating directly and voluntarily in them; - by ordering, advising, praising, or approving them; - by not disclosing or not hindering them…
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.