What was the Law an administration of?
The Law was an administration of death. Scripture states believers are delivered from that Law, which held them, so they now serve in newness of spirit, not in the oldness of the letter. This deliverance comes by believing the Gospel, not by legalism or fleshly effort, and it belongs to the spiritual realm.
Les explains that the Law was an administration of death, and since believers were held by it, they are now delivered from it. They should serve in newness of spirit rather than in the oldness of the letter. This transformation of life is in the spiritual realm. He contrasts this with the Galatian churches, where the flesh wanted legalism and Law. Having begun in the Spirit by Paul's Gospel through faith plus nothing, they were foolish to try to move into a deeper spiritual life by the flesh. The answer is to believe the Gospel.
But if the ministration of death, written and engraven in stones, was glorious, so that the children of Israel could not stedfastly behold the face of Moses for the glory of his countenance; which glory was to be done away: