Indeed, I was alive once apart from law; but when the commandment came, the sin [nature] revived and I died (Romans 7:9).
Death is separation, not annihilation; therefore, it is important to identify what a person is being separated from. Paul is referring to living out the life he now has in Christ. Having been co-buried with Christ and raised to walk in newness of life, he is now free to yield his members to righteousness. This participation in Christ’s death has freed him from the law, for a righteous man lives out from faith, not by law.
However, when Paul attempted to live again by the law—using the Mosaic commandments—he died, because the sin nature was revived. The law actually gives the sin nature strength to rule over a person (1 Corinthians 15:56). Therefore, when Paul sought to live out his life in Christ through the law, the sin nature made it impossible, separating him from the ability to live out from faith.
We do not use the law to govern our lives; rather, we live out who we are in Christ, thereby having no need for law, because in doing so we are living a righteous life out from faith—something that cannot be accomplished through law, for the sin nature makes it impossible.