Abstract: Group ostracize members. Sometimes they do it to enforce welfare-maximizing norms, but other times ostracism reduces welfare. Japanese villages have long used ostracism as a tool for conformity, and the targets have sometimes sued in response. The cases that have reached the courts disproportionately involve welfare-reducing behavior by the community; for example, ostracism against targets who report corruption. The targets usually win the civil cases against ostracizers and prosecutors usually win the criminal cases. Yet the targets seem not to have sued for financial or injunctive relief, and the prosecutors seem not to have pushed for prison terms. Instead, they have used the courts for an informational end: to certify and publicize innocence. This end is of minor importance in normal litigation, but crucial fo ostracism, as we explain using a formal model. We use case examples and the model to explore the factors that cause disputes to lead to ostracism and ostracisms to lead to litigation.