When Adam broke the Law, he brought death -- the curse of that broken Law -- upon all his posterity. None of them have escaped the curse. No one born of Adam will ever escape it. It will prosecute their cases unto death -- whether they are in the First Adam, or in the Last Adam, Christ.
When the Law prosecutes its case against a man in the First Adam, the doom is temporal and eternal death. The smoke of conscious torment will go up forever and ever.
But, when the Law prosecutes its case through the death of the Last Adam, then Christ and all those who are in him endure the eternal penalty (Christ for us) and rise on the other side triumphant, exempt forever from any further prosecution for sin.
The varying relationships to Law reflect the Two Covenants with the Two Men -- Adam and Christ (Rom 5).
God was served in the old way in Adam. The Law is the "husband" of those in Adam. Their works, fathered by the law, were holy, just and good -- until sin was brought in. Sin brought death. Then, the Law -- holy, just and good -- "fathered" the offspring of increasing rebellion in the rebellious offspring of Adam.
But God is served in a new way in Christ. The resurrected Christ is the "husband" of those in him, powerfully bringing forth in us the fruits of life. In him we have already triumphed over the death dealt out for our sins, and through the Spirit the dominion of sin is now broken. We are triumphing over our sins now -- and will triumph fully in the end! (Rom 7-8).
This transition of headship from Adam to Christ, which is a transition in relationship to the Law of God, is the deliverance from that relationship to the Law that Paul talks so much about.
The benefit of Christ is applied by God retroactively to all believers back to Adam, but the real deliverance from the curse (which did impend over all those ancient saints) did not take place until Christ did his work. The glory of this work issues in the advent of the Spirit in a new way in the saints of God, glorifying them with the glory of God's grace in life by the Spirit.
So, have we done away with the Moral Law? Surely, the new husband we have -- the author of the Law -- will bring forth fruits in us by his whole Word and Spirit, which are in accordance with his Law. The righteousness of the Law will be fulfilled in us who walk in the New Way by the Spirit (Rom 8).
Is it possible for believers to walk in the Old Way? Actually they cannot, but I think they can try. However, they will be very unhappy. They may find themselves more and more depressed and burdened by their sins. They may wonder if they know the Lord.
But, the calculus of sanctification is not, at root, measured by the degree of conformity to the Law. It is measured, first of all, by faith in Christ our husband. Sanctification is a gift to such as these. It cannot be earned by our works.