A common misconception is that God sold us as slaves to sin as a result of the trespass of Adam in the garden. Many think that this was part of his punishment. However, the scriptures teach that Adam sold himself into bondage when he disobeyed God's direct command. As a result the rest of mankind was also part of the package. We were delivered lock, stock and barrel to Satan's kingdom when the dominion and authority of the world was transferred to him. And the result is that God gets blamed for a lot of things that are no fault of his. Truth be told, the fault was ours.
It was always God's plan from the very beginning to fellowship with us face to face. The Bible says that He walked and talked with Adam and Eve in the cool of the evening. Even after the fall, he continued to fellowship with Adam, Eve and their children. He created us in His very own image and gave authority over all of creation and every living being to us. But everything was ruined with the introduction of sin because that dominion was given, by Adam to Satan. Humankind cascaded downward until the law was given to show us how sinful we were in comparison to God's holy standard. It was the awareness of that standard that separated us from God.
Therefore, the law is good, but Paul goes one step further to let us know that the law is also spiritual. We are by nature carnal and unspiritual because of what happened in the garden. Which means that the law is perfect but we are not nor could ever be. If we could have lived up to that perfect, holy standard then we would have obtained salvation by it. But since we are carnal and slaves to the default nature of this world it is impossible for us to obtain salvation by fulfilling the law. The result being death because we could not earn salvation by it.
Jesus on the other hand was perfect. He was born in the flesh as a hostage to the kingdom of darkness but since he was perfect he was able to fulfill the law in it's entirety. Because of this, he was able to redeem everything that was handed over to Satan in the garden. By faith, we can obtain the righteousness of the law that was impossible to obtain in the flesh. Romans 8 says, "in order that the righteous requirements of the law might be fully met in us, who do not live according to the sinful nature but according to the Spirit" ( Romans 8:4 ). The key is living by the Spirit of God and putting your trust in him. By faith we have all the benefits of Jesus fulfilling the law.