The one year limit should not be taken lightly because thereafter it will be impossible to convert the non-EU licence and driving with it will be considered as driving with no licence at all. It mighth be possible to fast talk the cops a few times but if it does not work the driver could be prossecuted. Driving with no licence is a criminal ofence with a possible outcome of up to 1 y. of prison and/or a fine up to € 15.000. "Récidive" (repeating the ofence in the next five years) can lead to even harsher sanctions. Nowadays in France there is an increase of cases involving drivers with no licence (and no insurance) and the authorities have opted out for the hard line policy...