Biblical Law serves many purposes; it shows our failures, our need for a redeemer, and even how to live in light of the Gospel. But it cannot save. Only he can.
Often, we see the law as a burden and don't like the way it convicts us. In Nehemiah, however, we are told to find joy in the law because, "the joy of the LORD is your strength."
The entire Law written in the Old Testament still holds just as much authority for us today, as affirmed by Christ, who came not to abolish the Law but to fulfill it.