I argue that rejection cannot be reduced to assertion. Adapting an observation by Huw Price, I argue that rejection is best conceived of as the speech act that is used to register that some other speech act is (or would be) violating a rule of the conversation game. This can be understood as registering norm violations where speech acts are characterized by their essential norms. However, rejection itself cannot be characterized by a norm. Instead, registering violations is a necessary condition for grasping the conversation game. The core observation is that the concept of an ‘illegal move’ is intelligible, so a speech act can be (say) an assertion, despite violating the essential norm of asserting. Rejection has the function of pointing out that a move is illegal. Registering rule violations is a precondition of playing games with rules (it is part of the concept ‘game’), not itself a rule in a game. A similar special role of rejection (that it is not explicable in the terms provided by a conceptual framework, but needed to grasp these terms) likely occurs in other frameworks as well, e.g. when one characterizes speech acts by commitments or their effect on a common ground.