If the Law could give life, how would righteousness be obtained?
If the Law could give life, righteousness would be obtained by the Law. A person would have to fulfill all its demands, and since the Law is perfect, anyone who kept all ten commandments would meet God's requirements and be accepted. But no person can do it except Christ.
Les explains that Paul is asking whether the Law is against God's promises. He then reads that if a law had been given which could have given life, righteousness would have been by the Law. The Law was perfect; all the demands of the Holy God were in the Ten Commandments. If a human being could have kept all ten, God would have let him into Heaven because he would have met God's demands. The problem is that no person can do it. Nobody can keep those Ten Commandments other than Christ Himself. So righteousness cannot come by the Law, because no one can fulfill it.
Is the law then against the promises of God? God forbid: for if there had been a law given which could have given life, verily righteousness should have been by the law.