Legitimate authority and obedience

Obedience is commanded within the limits of due observance. The duty develops according to the gradation of authorities which have power, not only over temporalities, but also over the conscience. St. Paul says, “let every soul be subject unto the higher powers, for there is no power but of God.” Therefore a Christian should obey power that is from God, but not otherwise.

Power may not stem from God for two reasons: it may be defective either in its origins or in its exercise.

Concerning the first, the defect may lie either in the personal unworthiness of the man or in some flaw in the manner of obtaining high position—violence, bribery, or some other illicit practice. The former is no bar to the possession of legitimate authority; and because the duty of obedience, it follows that subjects are bound to obey such a ruler, though as a man he is a good-for-nothing. The latter, however, is a bar, for a man who has snatched power by violence is no true superior or lord, and whoever has the ability may rightly reject him, unless perhaps the power has been subsequently legitimized by the consent of subjects or by higher authority.

The abuse of power may take two directions. Either the ruler imposes what is contrary to the purpose for which authority is instituted, for instance if he dictates vices contrary to the virtues authority is supposed to promote and sustain. In that event, not merely is a man not bound to obey, he is also bound not to obey, following the martyrs, who suffered death, rather than carry out the wicked decrees of tyrants. Or the ruler may make demands where his warrant does not run, for instance in exacting tributes to which he has no title, or something of the sort. In such cases a subject is not bound to obey, neither is he bound not to obey.

~St. Thomas Aquinas: Commentary, II Sentences, XLIV, ii. 2.
(Selected and translated by Thomas Gilby)

Allegory of the Good Government, by Ambrogio Lorenzetti.
Fresco, 1338-40; Palazzo Pubblico, Siena.