In his "Disseration on Divine Justice" John Owen takes aim at the heretical Socinians who deny penal substitution. He also seeks to straighten out some of the Reformed orthodox who were weakening the atonement by holding to the "hypothetical necessity" of Christ's sacrifice to satisfy divine justice.
Rutherford, of all people, held that "punitive justice" was "a free act of the divine will." Owen sees this as a necessary act of the immutable divine nature. God is free to provide a substitutionary atonement for sinners, or not. But God is not free to leave sin unpunished. So, having chosen to save sinners it was necessary that their sins be punished by way of substitution in the death of Christ.
As he discusses the divine nature, attributes and will, Owen makes some interesting comments about the truthfulness of God's speech:
But to me these arguments are altogether astonishing,--namely, "That sin-punishing justice should be natural to God, and yet that God, sin being supposed to exist, may either exercise it or not exercise it."
They may also say, and with as much propriety, that truth is natural to God, but, upon a supposition that he were to converse with man, he might either use it or not...(p. 507)
Supposing, as I said before, that his will were to speak any thing, it is necessary that he speak the truth. (p. 511)
For it being supposed that God were disposed to speak with man, he must necessarily speak according to truth. (p. 512)
The Works of John Owen: Volume 10