Article 666 of the French Civil Code
Any fence which separates hereditaments is deemed to be joint, unless there is only one of the hereditaments in a state of enclosure, or if there is a title, prescription or mark to the contrary. For ditches, there is a mark of non-jointness when the levee or discharge of land is on one side only of the ditch. The ditch is deemed to belong exclusively to the person on whose…