Moreover, a person turned away from communion is not, precisely, excommunicated. An excommunicated person cannot receive any Sacrament, including Matrimony, Anointing, or Penance, unless the excommunication is lifted.
In contrast, a person denied Communion could presumably return to Communion following repentance and a good Confession (Penance).
But I'm no canonist. I could be wrong. Is that right, Arthur?
That sounds right to me. I would add though, that a public sinner like a pro-gay marriage politician, would also need to publically repent before receiving communion again.
Please see post 16 of this thread.