The Préfet de département or, in Paris, the Préfet de police or, in the département of Bouches-du-Rhône, the Préfet de police des Bouches-du-Rhône may determine by decree, in certain communes and without prejudice to acquired rights, the distances within which 3rd and 4th category on-trade premises may not be established in the vicinity of existing premises in the same categories.