Do church membership, baptism, communion, or good works cancel the work of the cross?
Yes. Church membership, baptism, the Lord's Supper, and good works, when tied to salvation, cancel the work of the cross. God is adamant that He finished everything needed. Christ becomes of no effect to anyone justified by law, legalism, or fleshly effort, and such a person falls from grace.
Les teaches that circumcision was the immediate issue Paul addressed because Jewish teachers were bringing it into Gentile churches, but the principle applies to anything done in the energy of the flesh. Joining the church, being baptized, taking the Lord's Supper, or good works, as long as you tie it to salvation, cancel the work of the cross. God is adamant that He finished everything that needed to be done; if we are not satisfied with that, He is not accepting us. Paul repeats that circumcised persons become debtors to do the whole law, which only Christ could do. In verse 4, Christ becomes of no effect; He cannot touch us as long as we try to do something in the energy of the flesh. Falling from grace does not mean saved and fell out, but turning one's back on what God has provided.
Christ is become of no effect unto you, whosoever of you are justified by the law; ye are fallen from grace.