25 As men are by the will of God born for civil union and society, and as the power to rule is so necessary a bond of society that, if it be taken away, society must at once be broken up, it follows that from Him who is the Author of society has come also the authority to rule; so that whosoever rules, he is the minister of God. Wherefore, as the end and nature of human society so requires, it is right to obey the just commands of lawful authority, as it is right to obey God who ruleth all things; and it is most untrue that the people have it in their power to cast aside their obedience whensoever they please.
Source: Humanum Genus (Vatican.va)