Legal historians discuss the use they can make of Hart’s Concept of Law to study the emergence of law in ancient polities. The former saw oral customs as a form of spontaneous law at the origins of any legal development in ancient peoples. The demarcation made by Hart between pre-legal and legal systems can be used to differentiate customs outside legal systems and customary law inside legal systems. Legal historians are very attentive to the issue of writing down primary rules of conduct: archeological research that has no written testimonies cannot provide much information about customary laws; we can know customs of the past, as well as customary laws, only thanks to written texts. Legal historians are aware of two well-known historical situations, that of Icelandic Law and that of Athenian law, in which the tradition speaks of a supposed long period of oral customary law preceding the writing down of the law.