In the Trinity, the law is perfectly embodied by the Son, who is the uncreated Word and Wisdom and Rationality of the Father, in Glory equal, in Majesty coeternal. In the Godhead, therefore, God is neither above the law in essence, nor under his own law. If he were above his law, he would be arbitrary in his rule, capricious like the prophecies of Muhammad; if he were under his law, he would no longer be God, for his law would be God over him. Instead, when God made promise to Abraham, because he could swear by no greater, he swore by himself.
A mortal king, however, rules under the law. For though he embodies the law of the realm, and therefore has a special place in relation to the law, he is responsible to the laws of his fathers and especially to the law of God, who ever remains his sovereign, with imperium as well as auctoritas.