I'm not Roman Catholic, so please forgive my ignorance, but this seems pretty close to "You're not coming to our church, Sen. Kerry." Does denial of Holy Communion stop just short of ex-communication?
Everyone is welcome to worship the Lord with us.
But to recieve the Lord's Body and Blood (or any of the other Sacraments) one needs to show that he is of one mind with the Church regarding that Sacrament.
You can't receive Baptism if you do not believe in our doctrine of Baptism and the Trinity.
You can't receive Absolution during Confession if you do not beleive that Jesus personally forgives your sins when you repent and confess your sins to a priest, and commit yourself to avoiding sin in the future.
You can't recieve the sacarament of Confirmation unless you declare your desire to be sealed with the Holy Spirit and serve Christ as an adult Catholic.
You can't be married unless you declare that you believe marriage is sacred bond that lasts forever and agree to raise your children as Catholics.
You can't recieve ordination to the priesthood unless you declare obedience to the bishop, etc., etc.
When facing imminent death, you can't recieve the final annointing ("Last Rites") if there is no evidence that you are Catholic or wanted to be.
Technically, I don't think this is excommunication.
It is with holding of the Eucharist (Communion).
It certainly smells a lot like excommunication, and while it may not be so technically, it is a functional equivalent.