This chapter discusses the relationship of kinship rules to societal laws and argues that in tribal societies with prescriptive rules of marriage, kinship classification rules are like the societal laws Alexander has in mind, and they serve the same purpose. Where female mates are scarce and difficult to obtain, kinship classification and misclassification are conceptual tools used by adult males in the general arena of mate competition. Yanomamo mortality patterns are such that individuals are unlikely to have living, coresident genetic parents by the time they are 20 years old. Yanomamo fathers not only break the rules on behalf of their sons' reproductive success, they also encourage them to learn genealogies and the rules of classification as accurately as possible so they can do it for their sons. Adult male informants are more accurate in classifying their matrilateral than their patrilateral kin, suggesting that adult male manipulations of kinship classification are biased toward the patrilateral side.