Literally, “not under law.” The definite article “the” is not used with either “law” or “grace” (see on ch. 2:12). Paul is not referring here primarily to any law in particular but to law as a principle. His point is that Christians are not under law as a way of salvation, but under grace. Law cannot save a sinner, nor can law put an end to sin or its dominion. Law reveals sin (ch. 3:20), and because of the sinfulness of man, law, as it were, causes transgression to increase (ch. 5:20). Law cannot forgive sin, nor can law provide any power to overcome it. The sinner who seeks to be saved under law will find only condemnation and deeper enslavement to sin. Wherever the principle is held that man can save himself by his own works, there is no effective barrier against sin (DA 35, 36).

 But the Christian does not look for salvation legalistically, as if he could be saved by his own works of obedience (ch. 3:20, 28). He acknowledges that he is a transgressor of the divine law, that in his own strength he is wholly incapable of fulfilling its requirements, that he justly deserves to be under its condemnation, and surrenders himself through faith in Christ to the grace and mercy of God. Then, by the grace of God (see on v. 24), his sinful past is forgiven and he receives divine power to walk in newness of life. When a man is “under law,” despite his best efforts sin continues to have dominion over him, because the law cannot set him free from the power of sin. Under grace, however, the struggle against sin is no longer a forlorn hope, but a certain triumph.

 The offer to be under grace, thus to have victory over sin, and the enabling power for the attainment of every virtue, have been extended to every one of the descendants of Adam (John 3:16). But many have blindly or stubbornly chosen to remain under law. Even many who profess an earnest desire to be saved prefer to remain under law, as if they could commend themselves to God and earn salvation by their own obedience to law. Such was the experience of the Jews, and such is the experience of many professed Christians today, who in their pride of self-righteousness are not willing to acknowledge their own helplessness and to surrender themselves wholly to the mercy and transforming grace of God.

 Paul is saying that as long as a man is under law he remains also under the dominion of sin, for law cannot save one from either the condemnation or the power of sin. But those who are under grace receive not only release from condemnation (Rom. 8:1) but also power to overcome (ch. 6:4). Thus sin no longer will have dominion over them.

Or, “not be master.” It is true that sin will tempt and annoy. Nevertheless, it will not have mastery over the true Christian. Therefore, the believer should yield himself with courage to the service of God, for victory over sin is promised him.