In relation to the Law our union means that we are free from it as the governing principle in our Christian life. We are now under Grace and not the Law. Does that mean that the Law was bad? Paul says no! The Law is good and holy. The Law reflects God's Holy character, so it is not bad, it is good. Paul tells us that it is our sin, that makes the Law bad, because we can not keep God's holy standard. Some say that there are over 600 laws in the Old Testament given by God, they are summarized by God in the Ten Commandments and Jesus breaks them down even further to two in Matthew 22:34-40, telling us that the greatest Commandment of God is to love the Lord our God with all your heart and with all your soul and with all your mind and the second is you shall love your neighbor as yourself. Some think that we can write off the Ten Commandments today because we are not under Law but under Grace, that is a misunderstanding, God's Law is God's Law, it still reflects His character, and we are bound to obey His Law.
Our problem with the Law is that it exposes our sin. That is that purpose of the Law, to show how sinful we really are. How far away from God's perfect holy character we stand. It is to frustrate us to the point that we know deep within our souls that we are helpless to keep it and that our union with Christ is our only hope.
Romans 7 expresses the conflict in the believer. This conflict is between our remaining sin, and our new desire to be obedient to Christ. The constant fight between the old man and the new man. Paul says even when I want to do right, I find within me sin which wants to do wrong. This is the Christian experience. Some may ask how is it that the power of sin has been broken and I still have sin in me to the point that Paul can say what he says. Paul is describing the reality of our situation, the power of sin has been broken, if it had not been broken, your life would have continue as before, all you do and all you can do is sin. For the Christian, that is not so, you have the ability to resist sin, there are opportunities to escape temptations to sin, given by God. Our remaining sin is not a license to continue in our sin, we are to fight against it, but just as Paul tells us in asnwer to the question he asked "Wretched man that I am! Who will deliver me from this body of death? his answer and our answer is "Thanks be to God through Jesus Christ our Lord! That should be our attitude, we want to serve Christ and we must serve Christ, yet sin is still in us. This is the way that God has left us, and we know that it is to work in us Christlikeness, our struggle against Satan, the World and yes our own flesh, the old man, is a fight that will lead us to glory, that's why Paul and the other disciples could stand up and say to rejoice in infirmities, rejoice when you are being presecuted. Our attitude in our troubles, our pains, our grief, are not to be unfeeling or uncaring, NO! we should cry from our pain and other's pain, we should mourn and express our human sorrow, but we are to be held up but the fact, that we know that God is in control and He is leading us to glory, the Devil cant stop Him, and our own sin cant stop Him. We need rejoice, because our eyes have seen, and our hearts understand and are being held by the glory of God in the face of Jesus Christ and we are being transformed by that glory, degree by degree. Dont let your sin frustrate you, confess your sin and repent, plead with God for strength to fight sin even more. Get in line with God's program. Even though sin is still there, it was God's choice to leave it there, Christ is stronger than your sin. Pursue Christ in His word, and through prayer, until Christ becomes more satisfying to you than your sin. That is God's purpose, not to stay in our sin and say that God left me this way and use it as an excuse to indugle in your sin. God knows our heart at the deepest level your attitude will be exposed. No, we are to see the beauty of Christ more and more and see the hell of our sin more and more. The remaining sin in us should and will drive us to Christ.