So what does the law actually say?
A French urban legend says you must halt for three seconds at a Stop sign, but that isn't quite true. There is nothing in the law that identifies a specific duration. That said, the law states you have to come to an actual stop before the big thick white line on the road, meaning your wheels must not be moving forward.
Article Art R 415-6 in the Code de la Route specifically says: “At certain intersections indicated by a so-called Stop sign, all drivers must make a stop at the junction.