The U.S. Bishops have adopted a statement called "'Happy Are Those Who Are Called to His Supper': On Preparing to Receive Christ Worthily in the Eucharist."
The document says that a Catholic who "knowingly and obstinately" rejects "the defined doctrines of the church" or repudiates "her definitive teaching on moral issues" would not be in communion with the church and therefore should not receive Communion.
The interpretations I've seen say that politicians who persit in voting counter to church teachings on abortion, homosexuals who continue to engage in homosexual sex, people who regularly use artificial means of birth control, should not receive.
That cuts down on the number of communicants!
But, isn't that how it should be? Shouldn't we be worthy of Communion? Yes, I know it has a grace-filled healing effect, so it could be argued that receiving is a way to turn us from our sins, but if we obstinately
refuse to follow these teachings, then we should not receive.
And if we think these teachings are not valid, well, then we should go find a church whose teachings we can follow. Maybe even start one of our own, as the folks at Corpus Christi (now Spiritus Christi) Church in Rochester did.