Understanding “border” as a spatial marker delimiting the area of validity of a sovereign legal order no longer satisfactorily accounts for new forms of articulation between space and politics. Under the blows of globalization, regional integration, and separatist claims, borders are, today, undergoing profound transformations that affect their forms as well as their functions. Therefore, a border must be seen as a social construction, the product of social relations and powers, sometimes characterized by cooperation ties, sometimes designed by forms of opposition between the actors involved. The notion of border can thus benefit from the tools of sociology. It is no longer conceived, as envisaged by international law, as unique, linear and intangible, but on the contrary as multiple, reticular and fundamentally mobile.