Romans 3:19-20 (NIV)
19 Now we know that whatever the law says, it says to those who are under the law, so that every mouth may be silenced and the whole world held accountable to God.
20 Therefore no one will be declared righteous in his sight by observing the law; rather, through the law we become conscious of sin.

Romans 3:27-31 (NIV)
28 For we maintain that a man is justified by faith apart from observing the law.
29 Is God the God of Jews only? Is he not the God of Gentiles too? Yes, of Gentiles too,
30 since there is only one God, who will justify the circumcised by faith and the uncircumcised through that same faith.
31 Do we, then, nullify the law by this faith? Not at all! Rather, we uphold the law.

Paul is having to explain the relationship between law and grace. It would seem an easy subject at first glance, however it goes at the heart of the gospel and why the Messiah came to this earth. It is not as easy as it would seem. At least half of the subject in the book of Galatians has to do with law and grace. Notice the question in verse 31, "Do we, then, nullify the law by this faith?" If it is of faith then it is of grace and law has no place where there is grace. Therefore the law which was held up by Moses, David, and the prophets is nullified. This argument would be put forth by any good Jew. Jesus said this about His relationship about the law, "Do not think that I have come to abolish the Law or the Prophets; I have not come to abolish them but to fulfill them." Matthew 5:17. The key to understanding law and grace is to understand why Jesus came to this planet. Jesus is the fulfillment of the O.T. prophecies. The O.T. is all about Jesus first and seconding coming. We need righteousness and we cannot do this ourselves even with the knowledge of the law. The law in truth aggravates our situation; it does not heal us. The law sheds light that we need help but it does not do the saving. Later Paul will show how this was true even for Abraham. Abraham believed and it was counted to him as righteousness. One of the things that the Jews had forgotten is the relationship between the law and their own faith in Yahweh. It is my contention that the Jews placed the law ahead of God and that relationship which was to be supreme. The Jewish teachers simply were the keeper of rules instead of helping them seek God with all their hearts. In a way the Jews were committing idolatry with the law. They were placing it ahead of God. Today you can thank God that there is more understanding about grace on this side of the cross. However, the battle rages on as there are those who try to bring the law back to a position that is not Scriptural. Let Jesus reign in your life and all will be fine.