 It is sometimes claimed that in addition to structure, function and culture, social institutions necessarily involve sanctions. It is uncontroversial that social institutions involve informal sanctions, such as moral disapproval following on non-conformity to institutional norms. However, some theorists, e.g. Jon Elster (1989: Chapter XV), argue that formal sanctions, such as punishment, are a necessary feature of institutions. Formal sanctions are certainly a feature of most, if not all, of those institutions that operate within a legal system. However, they do not appear to be a feature of all institutions. Consider, for example, an elaborate and longstanding system of informal economic exchange among members of different societies that have no common system of laws or enforced rules.