Catechism of the Catholic Church §2240 — excerpt
Submission to authority and co-responsibility for the common good make it morally obligatory to pay taxes, to exercise the right to vote, and to defend one's country:
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: Ad Diognetum 5, 5 · 10 · 6, 10: PG 2, 1173 · 1176