Juries and other lay tribunals are often justified because they leaven the law with community norms. Unfortunately, we do not have a particularly good theory of when and how juries substitute their normative judgments for the law. A first step in developing such a theory is to examine the nature of norms and the way jurors bring normative judgments to their task. In this article I compare and contrast different understandings of norms that currently are in vogue in the social sciences and then use these approaches to develop a more systematic understanding of when juries do and when they do not substitute their normative judgment for that of the law.