Abuse of power is permitted by God and therefore the power is said to be “from God;” not, however, because God permits sin, for this would mean that the sin would be from God. Indeed, evil power is understood to exist by the permission of God because, since God is the author of the authority itself, which should not be thought of as a sin; He is not the approver of its abuse: And since this discussion is specifically about secular authority, it should be known that there are two things which, like two pillars, support good authority and without which no authority is approved: namely, legitimate institution and the moderation of justice. And indeed, legitimate institution revolves around three things: namely, the institutor, the one instituted, and those over whom he is instituted. Regarding the one who institutes, that he have public authority to institute, such as an emperor, a prefect, and the like; regarding the one instituted: that the person be suitable to be adorned with the cingulum [sword-belt, a Roman symbol of authority] of secular power, for example, not a regular cleric but a zealous layman; regarding those over whom it is established: that secular power rule over laymen, not to be placed over the hierarchy of clerics. The moderation of justice, however, is determined by five articles: according to the person, according to the cause, according to the measure, according to the place, and according to the time. According to the person, something is or is not permitted to the secular power: for example, it is permitted to lay hands on a layman if he sins, but not on a cleric. Justice is regulated according to the cause, so that secular, not spiritual, matters are examined by earthly authority. It is regulated according to measure or mode: when every offense is punished with a penalty that is fitting and appropriate to it, so that neither private hatred adds to a sufficient penalty nor private affection diminishes the proper severity. Justice is determined according to place, that is, where it is fitting for judgment to be exercised and honor shown to venerable places: so that in a church no one accused is punished, nor is a fugitive dragged from it to be handed over to corporal punishment. According to the timing: that reverence be shown on sacred and solemn days, so that even those who deserve punishment for their sins may be spared on these days.

-Rufinus the Decretist, Summa Decretorum (c. A.D. 1159)