Why do people want legalism?
It is part of the old Adamic nature to want to be under some kind of law. The flesh craves legalism, as shown by the Galatian churches. This desire resists serving in newness of spirit and instead returns to the oldness of the letter.
Les explains that believers are delivered from the Law, which was an administration of death, so they should serve in newness of spirit, not in the oldness of the letter. Yet the flesh still wants legalism. He points to Galatians 3:3, where Paul asks if having begun in the Spirit, they now seek a deeper spiritual life by the flesh. The Galatian churches desired legalism, and Les says it is just part of the old Adamic nature to want to be under some kind of Law.