For the sin [nature] taking occasion through the commandment, thoroughly deceived me, and through it killed (Romans 7:11).
Law does not bring life; it brings death because of the sin nature. The sin nature uses the principles of law to separate us from living out the life we have in Christ by appealing to self-effort, thoroughly deceiving us into a form of righteousness based on what we do, rather than on who we are in Christ.
There is a certain comfort in the law, for through it we are instructed concerning what not to do. However, the grace believer lives out his righteousness in Christ through faith. Since the law is not out from faith and only addresses what is to be avoided, living by faith cannot be accomplished through any aspect of law that restricts one’s actions under the perception of righteousness. For law is not out from faith.
In contrast to living by law, the grace believer is to use the renewed mind to discern between what is proper and what is wrong, knowing the desirous will of God and therefore acting in a mature manner. This kind of lifestyle flows from living out who he is in Christ, and thus does not allow the sin nature to thoroughly deceive him into using law as a gauge of righteousness.