How many times have you heard someone claim that "Rules and regulations, do's and dont's, these don't apply to me—I'm under grace!"? While it would be too damning to call them antinomians (some may just be too punch-drunk on the notion of grace), I believe the preceding sentiment is really born out of the ignorance of the enduring significance of the law in the life of the Christian. If the law is the expression of God's moral will, then as long as God endures, the law follows suit.
Dr. Joel Beeke, talking about Calvin's doctrine of piety, offers some profitable insights on the matter:
"To promote piety, the Spirit not only uses the gospel to work faith deep within the souls of his elect, as we have already seen, but he also uses the law. The law promotes piety in three ways:
1. It restrains sin and promotes righteousness in the church and society, preventing both from lapsing into chaos.
2. It disciplines, educates, and convicts us, driving us out of ourselves to Jesus Christ, the fulfiller and end of the law. The law cannot lead us to a saving knowledge of God in Christ; rather, the Holy Spirit uses it as a mirror to show us our guilt, shut us off from hope, and bring us to repentance. It drives us to the spiritual need out of which faith in Christ is born. This convicting use of the law is critical for the believer’s piety, for it prevents the ungodly self-righteousness that is prone to reassert itself even in the holiest of saints.
3. It becomes the rule of life for the believer. 'What is the rule of life which [God] has given us?' Calvin asks in the Genevan Catechism. The answer: 'His law.' Later, Calvin says the law 'shows the mark at which we ought to aim, the goal towards which we ought to press, that each of us, according to the measure of grace bestowed upon him, may endeavor to frame his life according to the highest rectitude, and, by constant study, continually advance more and more.'" (Calvin's Piety, Mid-America Journal of Theology 15 , 45)