Children's understanding of rules was investigated by observing 5-, 6- and 7-year-olds engaging in unrestricted joint activity with familiar peers. Initially, all groups collectively regulated themselves by negotiating the invention and alteration of rules, hence demonstrating understanding of the consensual origins, relativity and mutability of their own rules. However, children who later returned to participate in second episodes often imposed their previously invented rules, as if they were unalterable and non-negotiable, on their new partners. This suggested a traditionalist, or conservative, orientation to rules, reminiscent of Piaget's claim that children do not differentiate moral and conventional rules. An explanation of the apparent inconsistency in children sometimes sounding heteronomous and sometimes autonomous is proposed that emphasises the role of social context in the production of discourse about rules. These findings are discussed with reference to those of previous researchers, including the domain theorists, who have asked children only about elders' conventional rules, and hence risked confounding respect for rules with respect for the imposers of rules. Children can say very different things about a rule depending on when, how and by whom it was established and applied.