Legal scholars have argued for years that trade secrets are the oldest set of intellectual property rights. However, formal protection for trade secrets only came to be after 1810 with the issuance of the Napoleonic Penal Code. This article argues that ancient civilizations, Roman law and medieval guilds did not perceive trade secrets as intangible property, but rather as a confidentiality obligation, and that, currently, the concept of trade secrets has not changed: its protection does not depend on the exercise of a right of property, but rather of an unfair act or the breach of a contract by a third party.