The Pope (Papacy) may excommunicate players.
"Excommunication (Latin ex, out of, and communio or communicatio, communion — exclusion from the [sacrament of] communion), the principal and severest censure, is a medicinal, spiritual penalty that deprives the guilty Christian of all participation in the common blessings of ecclesiastical society." Source: The Catholic Encyclopedia, NewAdvent.org.
The effect of being excommunicated last for one season. An excommunicated player cannot send nor receive messages from other players. If another player does communicate with the subject will be excommunicated.
The Pope may also call for a Crusade against the Turk. The same limitations apply to the Turk. Likewise, if another player does communicate with the Turk, they will be excommunicated.