Final installment of the piece...
So Paul certainly wanted his Jewish and Gentile audiences to conclude that the Gentiles did not need to keep the parts of the Law that related to specifically Jewish practices like circumcision (e.g., Gal. 5:2). With regard to Jews, he insisted that they should not keep purity rules that divided the body of Christ, such as when Peter and Barnabas stopped eating with Gentile believers at Antioch (Gal. 2:11-13). In this sense, he no longer considered himself to be under the Law, even though he was a Jew (1 Cor. 9:20).
Nevertheless, Paul saw the Christian as still being under Christ’s law (1 Cor. 9:21), what later Christians would call the “moral” law. Through the power of the Holy Spirit, he affirmed that Christians could now keep the “righteous requirements” of the Law. They were not “under Law,” which for Paul implied being under the power of Sin and the curse of sinfulness. They were now empowered, “set free from sin” and now “slaves to righteousness” (Rom. 6:18).
So do we “nullify the law by this faith” (Rom. 3:31)? “Not at all! Rather, we uphold the law.” We now keep the “moral” essence of the Law through the power of the Spirit. We do not “sin because we are not under law but under grace” (Rom. 6:15). Rather, we “do not let sin reign in your mortal body so that you obey its evil desires” (6:12). In a strange paradox, Paul affirmed that it is only when we are not under the Law that we can actually keep its righteous requirements.