Related Rule
France
Practice Relating to Rule 37. Open Towns and Non-Defended Localities
France’s LOAC Manual (2001) defines as an open town “any inhabited area located in the combat zone or in its proximity, which is open to enemy occupation in order to avoid fighting and destruction”. It lists the following four conditions that must be fulfilled in order for a town to be considered an open town: all combatants as well as mobile weapons and military material must be evacuated; no hostile use shall be made of fixed military installations and establishments; the authorities and the population shall abstain from committing any act of hostility; no activities in support of military operations shall be undertaken. The manual gives Paris in 1940 and Rome in 1943 as examples of open towns during the Second World War. 
France, Manuel de droit des conflits armés, Ministère de la Défense, Direction des Affaires Juridiques, Sous-Direction du droit international humanitaire et du droit européen, Bureau du droit des conflits armés, 2001, p. 124.
France’s LOAC Manual (2001) is guided by Article 59 of the 1977 Additional Protocol I as regards the conditions that must be fulfilled in order for an area to be declared a non-defended locality. 
France, Manuel de droit des conflits armés, Ministère de la Défense, Direction des Affaires Juridiques, Sous-Direction du droit international humanitaire et du droit européen, Bureau du droit des conflits armés, 2001, p. 31.
France’s LOAC Teaching Note (2000) includes non-defended localities among the zones that are specially protected by IHL. It states that, while occupation of non-defended localities is permitted, attacks against such localities are prohibited, provided they are completely demilitarized. 
France, Fiche didactique relative au droit des conflits armés, Directive of the Ministry of Defence, 4 January 2000, annexed to the Directive No. 147 of the Ministry of Defence of 4 January 2000, p. 5.
France’s LOAC Manual (2001) includes undefended localities in the list of specially protected objects and states that it is prohibited for the parties to a conflict to attack them by any means whatsoever. 
France, Manuel de droit des conflits armés, Ministère de la Défense, Direction des Affaires Juridiques, Sous-Direction du droit international humanitaire et du droit européen, Bureau du droit des conflits armés, 2001, p. 31.
The manual also prohibits attacks on open towns. 
France, Manuel de droit des conflits armés, Ministère de la Défense, Direction des Affaires Juridiques, Sous-Direction du droit international humanitaire et du droit européen, Bureau du droit des conflits armés, 2001, p. 124.
France’s Penal Code (1992), as amended in 2010, states in its section on war crimes related to international armed conflict: “Attacking or bombarding, by whatever means, towns, villages, dwellings or buildings which are undefended and which are not military objectives is punishable by life imprisonment.” 
France, Penal Code, 1992, as amended in 2010, Article 461-24.
The Report on the Practice of France states that attacks against protected zones are prohibited. 
Report on the Practice of France, 1999, Chapter 1.8.