Taking a step back, Communes are generally the lowest level of local governance in France, second only to small neighborhoods, called arrondissements, that only exist in really large cities like Paris.
Prior to a restructuring that was kicked off by the 1958 constitution, France had 2 tiers of local government (collectivités territoriales):
- Departments (départements)
- Municipalities (communes)
It wasn’t until 1982 that the Policy Of Decentralization introduced a third level of local government called Regions (régions). The goal behind their creation was to impede the central governments supervisory powers over the local authorities’. Essentially these regional designations were to act as a buffer between the central government and Departments.
So after 1982, local governance now had a new structure;
- Regions (régions)
- Departments (départements)
- Municipalities (communes)
The principle of freedom of administration by local authorities is explicitly enshrined in the French Constitution and society, and is completed by the principle of financial autonomy of the local, intermediate and regional authorities granted by 1982 decentralization reforms.
Besides the Constitution of 1958, the General Code on Local Authorities,
code général des collectivités territoriales, describes the competences attributed to the Regions, Departments and Municipalities.
With that context, let’s revisit the practical power or responsibilities regularly granted to the Municipalities (communes) to answer your question.
Local governance is addressed by both a Mayor (maire) and local Municipalities, who act as decentralized authorities. The two bodies delineate their powers as such.
The Mayor (Maire) is responsible for issues related to;
- Registry;
- Electoral issues;
- Social welfare (complementary action to that of the Departments);
- Education, including primary schools and pre-school classes;
- Local roads;
- Town planning, and
- Protection of public order
Decentralized authorities are tasked with;
- Municipal transport, including school transport, yacht harbors, civil airports, non-autonomous harbors;
- Culture, including teaching schools (écoles maternelles et primaires), archives, museums, libraries;
- Public health (vaccination);
- Economic development (complementary to that of the Region);
- Environment, specifically water and waste, and
- Housing.
Given the above, you can see how a commune like Rochefourchat would have legitimate responsibilities and powers, even if just one person is living in it. It is a historical site with the ruins of an old castle, and the preservation of that culture falls squarely in the hands of the Commune it is located in. It is fair that the responsibilities maybe small, but they are unique to the small commune, and not necessarily best outsourced to a larger decentralized body like Community of communes of Diois.
Outside of Rochefourchat, France likes to maintain other Communes with nominal populations for historical preservation.