Ostracism, as noted by vickyace, seems the apt word, but there's also shunning, a practice used by some religious communities, e.g., the Amish, to brand those who have violated social norms as outcasts with whom community members should no longer have any relations.
Another word that has religious overtones, but is occasionally used in other contexts is excommunicated.
E.g., dictionary.com lists one of the definitions for excommunicate to be "to exclude or expel from membership or participation in any group, association, etc." and as a usage example lists "an advertiser excommunicated from a newspaper."
