Related Rule
France
Practice Relating to Rule 45. Causing Serious Damage to the Natural Environment
France’s LOAC Manual (2001) restates the prohibition on employing methods or means of warfare which are intended, or may be expected, to cause widespread, long-term and severe damage to the natural environment set out in Article 35 of the 1977 Additional Protocol I. 
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. 63.
Upon ratification of the 1980 Convention on Certain Conventional Weapons, France stated:
The fourth paragraph of the preamble to the Convention on Prohibitions or Restrictions on The Use of Certain Conventional Weapons Which May Be Deemed to Be Excessively Injurious or to Have Indiscriminate Effects, which reproduces the provisions of Article 35, paragraph 3, of Additional Protocol I, applies only to States parties to that Protocol. 
France, Reservations made upon ratification of the Convention on Certain Conventional Weapons, 4 March 1988.
Upon ratification of the 1998 ICC Statute, France declared:
The risk of damage to the natural environment as a result of the use of methods and means of warfare, as envisaged in article 8, paragraph 2(b)(iv), must be weighed objectively on the basis of the information available at the time of its assessment. 
France, Interpretative declarations made upon ratification of the 1998 ICC Statute, 9 June 2000, § 7.
Upon ratification of the 1977 Additional Protocol I, France stated:
The Government of the French Republic considers that the risk of damaging the natural environment which results from the use of certain means or methods of warfare, as derives from the provisions of paragraphs 2 and 3 of Article 35 as well as those of Article 55, shall be examined objectively on the basis of information available at the time of its assessment. 
France, Declarations and reservations made upon ratification of the 1977 Additional Protocol I, 11 April 2001, § 6.
France’s LOAC Manual (2001) states:
The Stockholm Convention of 10 December 1976 (ENMOD), which has not been signed by France, prohibits the use of environmental techniques for military or any other hostile purposes. France has not adhered to this convention because it is of the opinion that it contains vague provisions which render its application uncertain, particularly with respect to nuclear dissuasion. 
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. 63.