27 You have more than once recalled to your Faithful that the Church protects peace and order, even at the cost of grave sacrifices, and that it condemns every unjust insurrection or violence against constituted powers. On the other hand, among you it has also been said that, whenever these powers arise against justice and truth even to destroying the very foundations of authority, it is not to be seen how those citizens are to be condemned who united to defend themselves and the nation, by licit and appropriate means, against those who make use of public power to bring it to ruin.
Source: Firmissimam Constantiam (Vatican.va)