The French retail industry is the most regulated in Europe. However, the recent Dutreil law, which took effect on January 1st 2006, lightens the regulation reforming the previous 1996 Galland law. The purpose of this reform is to lower retail prices of products sold in supermarkets, especially the prices of national brands. The research work presented here help define better the mechanisms that facilitate the rise, or conversely the drop, in retail industry prices. The balance of power between suppliers and retailers and the regulations play a crucial part in the understanding of these mechanisms. The analyses associate theoretical and empirical contributions.