Galatians 3:10-14 (ESV)
For all who rely on works of the law are under a curse; for it is written, "Cursed be everyone who does not abide by all things written in the Book of the Law, and do them."  Now it is evident that no one is justified before God by the law, for "The righteous shall live by faith."  But the law is not of faith, rather "The one who does them shall live by them."  Christ redeemed us from the curse of the law by becoming a curse for us—for it is written, "Cursed is everyone who is hanged on a tree"—  so that in Christ Jesus the blessing of Abraham might come to the Gentiles, so that we might receive the promised Spirit through faith.
For all who rely on works of the law are under a curse. It should be noted here that it is not all those who do works of the law, but those who rely on them. We all do works of the law. That can hardly be helped, anymore than the fact that we all sin. It isn’t that doing works of the law in and of themselves is bad, it is relying on works of the law for salvation. For instance, Paul is talking chiefly about circumcision, all though included in this is everything that goes along with this covenant. Most men in the western hemisphere today are circumcised as a matter of course, it is indifferent it neither detracts or adds from one’s salvation. Most people today tend to be law abiding citizens as Paul bids us to be in Romans 13. This whether or not they believe. Even atheists tend to be moral people by worldly standards anyway. One could make the case that by Christians standards they are immoral since they routinely break the third commandment. However, their works of the law do nothing for them. This is the same as for Christians. We tend to do works of the law, but these add nothing to our salvation. Faith makes the difference. The righteous live by faith, and that in the mercy of God on account of Christ. For it was He who redeemed us by becoming a curse for us. He lived the law for us, and was cursed by it for us. Therefore the blessing of Abraham came to us Gentiles in Christ Jesus, and we have received the promised Spirit through faith.