This paper proposes a semiotic theory of norms—what I term normative semiotics. The paper’s central contention is that social norms are a language. Moreover, it is a language that we instinctively learn to speak. Normative behaviour is a mode of communication, the intelligibility of which allows us to establish cooperative relationships with others. Normative behaviour communicates an actor’s potential as a cooperative partner. Compliance with a norm is an act of communication: compliance signals cooperativeness; noncompliance signals uncooperativeness. An evolutionary model is proposed to explain how this comes about: evolution has generated an instinctual proficiency in working with these signals much like a language—a proficiency that manifests in an emotional context. We see these social rules as possessing a certain ‘rightness’ in normative terms. This adaptive trait is what we call internalization. Internalization enhances the individual’s ability to speak this code. Because these signals communicate who is and who is not a reliable co-operator, sending and receiving cooperation signals is crucial to individual survival. Individuals who internalized the entire process and thus became more adept at speaking the language were at an advantage. Law seeks to shape the language of norms by maintaining the collective standards of society; as such, understanding how and why this normative language emerges is critical to understanding a core function of law.