What would people say about themselves if there were no Law?
If there were no Law, people would say they are good enough and that God will accept them. They would not see themselves as guilty, lost, or in need of salvation, because the Law is what condemns and reveals that they have broken the Ten Commandments.
Les explains that if it were not for the Law, anybody could say, "Well, I'm good enough, God will accept me." But the Law says you're guilty. He shares his pastor's comment that you can never be saved until you know that you're lost, and the way you know you're lost is because the Law condemns you. Since no one in the room has not broken the Ten Commandments, they are lawbreakers and therefore sinners. The Law was severe, demanding death for violations, and it had nothing to help man keep it. Only because of the work of the cross have we been set free from all of that, but the Law is what makes us realize why we needed salvation.