While one of the greatest achievements of the European Union, the ope­ning of internal borders, risks being canceled, it is opportune to go back to thinking about the nature and function of the border and, therefore, about the freedoms we might lose. Always tracing a border line means to perform an act of violence: think of the mythical foundation of Rome. But just like the State, private property also resorts to violence to define the contours of its rule: think of the fence of the common lands in England. This essay is a concise historical and political reconstruction of this ancient link between violence and borders.