[…] It is the age old question of God’s wise use of evil, yet this more than anything else provides the greatest demonstration of His unlimited power to accomplish His ultimate and highest purpose in glory. God’s ability to bring the greatest good out of the worst evil (Acts 2:23; Rev 13:8) is His glory. This ‘bright side of the dark picture’ is basis of hope in Isaiah, Habakkuk, Daniel, and all the prophets, since the gospel does not begin in the New Testament. That the glory of grace should be revealed against the backdrop of an undiminished severity of holy justice demonstrates something about the power and character of God that nothing else could ever do.
So yes, Satan is indeed ‘free’ in the sense that he is not coerced. However, in keeping with God’s over-ruling use of evil, Satan, like all created things, is perfectly “ruled over” in the sense of God’s sovereignty. As the wrath of man is made to praise Him (Ps 76:10), so too is the rage of Satan made to serve the plan of God. He is always made to hang on his own gallows and to fall into the snare that was prepared for the just (Prov 28:10; Est 7:10), as God has also prepared a snare for all pride, both human and demonic, in the prophetic mystery of Christ (compare Isa 8:14-15; 28:13 with 1Cor 2:7-8). […]