Article R2224-20 of the French General Code of Local Authorities
I. – Authorisation to implement a water pricing system that does not include a term directly proportional to the total volume consumed may only be granted if the total population of the commune, the public establishment for inter-communal cooperation or the mixed syndicate is less than one thousand inhabitants and if the water resource is naturally abundant in the sub-basin or in the groundwater used by the drinking water service….