Related Rule
France
Practice Relating to Rule 43. Application of General Principles on the Conduct of Hostilities to the Natural Environment
France’s Code of Defence (2004), as amended in 2008, states:
It is … prohibited [for combatants] to carry out an attack that may incidentally inflict widespread, long-term and severe damage to the natural environment which is excessive in relation to the military advantage anticipated. 
France, Code of Defence, 2004, as amended in 2008, Article D4122-10.
France’s Penal Code (1992), as amended in 2010, states in its section on war crimes related to international armed conflict:
Intentionally launching an attack in the knowledge that it will cause incidental … widespread, long-term and severe damage to the natural environment which would be clearly disproportionate in relation to the concrete and direct military advantage anticipated for the overall attack … is punishable by 20 years’ imprisonment. 
France, Penal Code, 1992, as amended in 2010, Article 461-28.
Upon ratification of the 1998 ICC Statute, France declared:
The risk of damage to the natural environment as a result 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.