Romans 6:14 For sin shall not be master over you, for you are not under law but under grace.
When St. Paul writes about not being “under the law,” he is not at that point teaching us that being Christian means being antinomian. The not being under the law that Paul is referencing here has to do with the freedom from the condemnation of the law that is a reality for all those outside of Christ. Man, as being mortal is always governed by some law and so it is literally not possible to be free from law in the sense of having a lawless existence.
Freedom from the condemnation of the law is the good news the Gospel brings. Outside of Christ, we are forever burdened by the accusation of God’s law that we are guilty of not keeping God’s law. In Christ, we are free from that accusation (and the condemnation following) that we are guilty of because of our violating God’s law, and we are free from the condemnation of God’s law precisely because Christ is the one, in His crucifixion, who, as our substitute, already received in Himself the penalty and condemnation that was properly designed for us due to our breaking of God’s law.
Having been set free from the condemnation of God’s law we are now at liberty to walk in terms of God’s law without any fear because there is therefore now no condemnation for those who are in Christ Jesus. We are those who no longer walk consistent with our sinful former appetites but who now walk according to our law honoring desires as we are new creations.
That God’s law still functions in our life is the great presupposition of Scripture. After all, how could we ever successfully honor the call to lay aside sin
in reference to your former manner of life, you lay aside the old self, which is being corrupted in accordance with the lusts of deceit,23 and that you be renewed in the spirit of your mind, 24 and put on the new self, which in the likeness of God has been created in righteousness and holiness of the truth. (Ephesians 4:22)
Therefore, since we have so great a cloud of witnesses surrounding us, let us also lay aside every encumbrance and the sin which so easily entangles us … (Hebrews 12:1)
unless there was a standard by which we could know whereby that sin is determined? If we are not under law in the sense that the law no longer exists for the Christian then there is no possibility for us to sin, since without law sin does not exist. If we are not under law in the sense that the law no longer exists for the Christian then right and wrong and good and bad really are only existential social constructs with the result that every Christian does what is right in their own eyes.