Critical responses to the application of Rational Choice theories to the study of religious phenomena tend to be polarized between outright denial that the theories have any relevance to religion and equally outspoken claims that the theories are the only hope for progress in the sociology of religion. Both of these extreme positions are avoided by raising a question, instead, about one of Rational Choice's central propositions about religion. This proposition holds that levels of religious vitality vary positively with the degree to which agencies of the state are prevented from regulating religious activity. The findings of recent research into prison chaplaincy in the UK and the US are used to test this claim. The main argument is that the existence of an established church has facilitated a higher level of religious activity, especially for minority faiths, in prisons in England and Wales than is possible in US prisons.