Bracketing the unnerving effect of some of the language in this piece, I'm in agreement that God is blessedly sovereign over all of life and that he does not owe something to sinful humanity. However, Piper doesn't clarify how God's actions constitute enactments of justice, righteousness, goodness. Does God willing something render that something a righteous action (so nominalism). Or, does God submit himself to an external standard of righteousness and then act accordingly (so hard realism)? This is a well-known issue in both philosophy and theology often called the Euthyphro problem. Neither option seems to be satisfactory inasmuch as God is neither capricious (pace nominalism) nor subject to anything external to God (pace what I would call a hard version of realism about universals like justice and goodness). In my mind, the appropriate response is to maintain that God is subject to a standard of goodness and righteousness, but that this standard is his own nature. To confess God's simplicity is, negatively, to hold that he is not composed of parts. To unpack this, God is not really distinct from any of God's perfections but just is, when viewed under a particular aspect, his corresponding particular perfection (holiness, omniscience, love, goodness, etc.). So God's essence is his own righteousness and this righteousness, internal to God, is the standard according to which God must act and does act in the world.
What does this mean for Piper's statement? It means that, while God is free to act how he pleases, not least in relation to rebellious sinners, he is, contra nominalism's doctrine of God's absolute freedom, not free to contradict his own goodness and righteousness. The pastoral and apologetical import of God's sovereignty is more firmly established if God's sovereignty is wedded to God's simplicity and his commitment always to enact his own goodness in all his dealings with his creatures.
Any thoughts on this?