The law and commandments can’t save us. They never made anything perfect. If you are trying to get to heaven by living by the law and commandments, you will fail. The law of carnal commandments as taught by the Aaronic Priesthood along with the doctrine of sin, repentance, baptism, etc. is part of the preparatory gospel. They are given to people who don’t have the Holy Ghost as their guide. (see D&C 84:25-27; 2 Nephi 32:5; Gal. 5:18,22-23; D&C 18:35; D&C 97:1)