How Does Freedom from the Law Entail Freedom from Sin?

Sinclair Ferguson, on Owen's theology of mortification:

How does Christ set us free from the law? And how does that freedom involve freedom from the dominion of sin?

For Owen the answers are clear: Christ sets us free from the curse of the law by taking that curse himself and he fulfills the demands of the law for holiness for the believer by his perfect life. . . . He is the believer's righteousness.

But how does freedom from the law entail freedom from the dominion of sin? It is because the believer's union with Christ, which effects his freedom from the law, also effects his 'death to sin,' for he is united to Christ both in his death under the law and his simultaneous death to sin. The two were inseparable in Christ, and through union with him, they are also inseparable in the Christian.

--Sinclair Ferguson, John Owen on the Christian Life (Banner of Truth, 1987), 130; italics original

That last paragraph is worth digesting. I believe it is deeply Pauline and right, and not frequently explained.