CCC 2240 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:
Pay to all of them their dues, taxes to whom taxes are due, revenue to whom revenue is due, respect to whom respect is due, honor to whom honor is due.1
[Christians] reside in their own nations, but as resident aliens. They participate in all things as citizens and endure all things as foreigners. .. They obey the established laws and their way of life surpasses the laws. .. So noble is the position to which God has assigned them that they are not allowed to desert it.2
The Apostle exhorts us to offer prayers and thanksgiving for kings and all who exercise authority, “that we may lead a quiet and peaceable life, godly and respectful in every way.”3
1 Rom 13:7.
2 Ad Diognetum 5, 5 and 10; 6, 10: PG 2, 1173 and 1176.
3 1 Tim 2:2.