Romans 7:5: While We Were Living In The Flesh, Our Sinful Passions, Aroused By The Law, Were At Work
 For while we were living in the flesh, our sinful passions, aroused by the law, were at work in our members to bear fruit for death. (ESV)
There is an amazing thing that happens in the heart of an unregenerate sinful man. When the sinful man encounters God's Law they are drawn to rebel against it. Instead of looking at the holy standard of purity as something to attain they become drawn to direct defiance of that standard. The Law does not make them holy, it arouses their unholiness even further.
If you question me consider a young child. When you tell them they are not permitted to do something you will find them wanting to do what you do not want them to do. Later in this chapter Paul will talk of his own struggle with the sinful nature. He tells us that the things he knows he should not do he finds himself doing. We are all wired that way.
This leads us to question whether the Law is effective in curbing man's sinful behavior. The answer is no. The Law can give punishments for those who break the Law. If those punishments are carried out it may keep people from committing some "breaking of the Law," but it cannot do anything to change the heart of man.
Our sinful passions only become aroused by the Law, not subdued. These sinful passions when pursued lead to eternal death. Understanding what Paul is saying is so important for us to understand. If we want to see people's lives changed for righteousness we must bring them to the one who can change their passions and give them a new heart. That is only found in Jesus Christ.
The Law, in itself, will not change your wicked heart. But it can show you how evil your heart is. Turn to Jesus who fulfilled the Law. Through him you can die to the Law and be born again by the Spirit. That is the only way to righteousness.