I’d like to add to my posting above, even someone who is excommunicated is not held to be relieved of his or her duties before God. One would still have the obligation to worship God, (ie assist at Mass on Sundays and Holy Days, say ones daily prayers, etc.) Excommunication is one of the penalties that can be placed on an individual or group, as is interdict and other canonical penalties. Much easier than in the Early Church. If you read the story of Ananias and Saphorah, as the Scriptures tell us Ananias was struck dead for his lie to the Holy Ghost, by telling untruths to the Apostles, he had lied to God.

In the early Church many people held off on baptism until near death, they believed, but did not become incorporated into the Body of Christ because the penalties imposed for sin where very harsh compaired to today. Various sins would be punished by the Early Bishops and the Apostles by being removed from the Liturgy with the Catechumens after the Liturgy of the Word and before the Liturgy of the Eucharist. If you assist at an Eastern Rite Liturgy, the deacon still chants, “All Catechumens depart” three times after the Gospel and Sermon… Penalties such as not being able to receive the Holy Eucharist sometimes for years or up until one was on their deathbed where also imposed. So the modernday practice of excommunication, with the possiblity of returning to the good graces of the community by the simple action of going to confession and renouncing ones errors are quite liberal compaired to the standards early Catholics had to face from the times of the Apostles through the first few centuries of the Church’s existance.