In a paper published in 2006, I argued that the best way of defending something like our current practices of punishing war criminals would be to base the justification of this practice on an expressive theory of punishment. I considered two forms that such a justification could take-a 'denunciatory' account, on which the purpose of punishment is supposed to communicate a commitment to certain kinds of standard to individuals other than the criminal and a 'communicative' account, on which the purpose of the punishment is to communicate with the perpetrator, and argued for a denunciatory account which I developed at some length. In this paper I would like to reconsider the plausibility of a communicative account. One difficulty that such accounts face is that the punishment of war criminals often involves the inflicting of harsh treatment on them by individuals who are members of states other than their own. On a communicative account this is problematic: on such an account-or at least on the version of it proposed by Duff (2000)-it is essential that those who are punish and those who punish them belong to a single community. When this requirement is not satisfied harsh treatment does not constitute punishment. Duff has argued that the problem can be solved by regarding all human beings as members of a single moral community: here I argue that this suggestion is unsatisfactory and propose an alternative. One consequence of my account is that if it is correct there may limitations on the range of kinds of war criminal that can legitimately be punished by international tribunals. © 2010 Springer Science+Business Media B.V.