It is actually part of a summary of Unan Sanctum by Denzinger. And I must say it agrees fully with with the New Advent Catholic Encyclopedia's summary:
Both swords are in the power of the Church; the spiritual is wielded in the Church by the hand of the clergy; the secular is to be employed for the Church by the hand of the civil authority, but under the direction of the spiritual power.
The one sword must be subordinate to the other: the earthly power must submit to the spiritual authority, as this has precedence of the secular on account of its greatness and sublimity; for the spiritual power has the right to establish and guide the secular power, and also to judge it when it does not act rightly. When, however, the earthly power goes astray, it is judged by the spiritual power; a lower spiritual power is judged by a higher, the highest spiritual power is judged by God.
This authority, although granted to man, and exercised by man, is not a human authority, but rather a Divine one, granted to Peter by Divine commission and confirmed in him and his successors. Consequently, whoever opposes this power ordained of God opposes the law of God and seems, like a Manichaean, to accept two principles.