18 And how are these political changes of which We speak produced? They sometimes follow in the wake of violent crises, too often of a bloody character, in the midst of which pre-existing governments totally disappear; then anarchy holds sway, and soon public order is shaken to its very foundations and finally overthrown. From that time onward a social need obtrudes itself upon the nation; it must provide for itself without delay. Is it not its privilege - or, better still, its duty - to defend itself against a state of affairs troubling it so deeply, and to re-establish public peace in the tranquillity of order? Now, this social need justifies the creation and the existence of new governments, whatever form they take; since, in the hypothesis wherein we reason, these new governments are a requisite to public order, all public order being impossible without a government. Thence it follows that, in similar junctures, all the novelty is limited to the political form of civil power, or to its mode of transmission; it in no wise affects the power considered in itself. This continues to be immutable and worthy of respect, as, considered in its nature, it is constituted to provide for the common good, the supreme end which gives human society its origin. To put it otherwise, in all hypotheses, civil power, considered as such, is from God, always from God: "For there is no power but from God."(9)
Source: Au Milieu Des Sollicitudes (Vatican.va)