Related Rule
Belgium
Practice Relating to Rule 43. Application of General Principles on the Conduct of Hostilities to the Natural Environment
According to Belgium’s Regulations on the Tactical Use of Large Units (1994), restrictions on the use of weapons can result from “the obligation to respect the rules of the laws of war relative to the conduct of hostilities. These rules concern, inter alia, the choice of means and methods of warfare, the protection of the civilian population, civilian objects and the environment.” 
Belgium, L’Emploi Tactique des Grandes Unités, Règlement G 119, Ministère de la Défense Nationale, Etat-Major Général, Force Terrestre, Sections Operations et Entraînement, 1994 (édition provisoire), Article 208(c)(2).
Belgium’s Penal Code (1867), as amended in 2003, provides:
War crimes envisaged in the 1949 [Geneva] Conventions … and in the [1977 Additional Protocols I and II] … , as well as in Article 8(2)(f) of the [1998 ICC Statute], and listed below, … constitute crimes under international law and shall be punished in accordance with the provisions of the present title … :
22. intentionally launching an attack in the knowledge that such attack will cause … widespread, long-term and severe damage to the natural environment, which would be excessive in relation to the concrete and direct military advantage anticipated. 
Belgium, Penal Code, 1867, as amended on 5 August 2003, Chapter III, Title I bis, Article 136 quater, § 1(22).
Belgium’s Law relating to the Repression of Grave Breaches of International Humanitarian Law (1993), as amended in 2003, provides:
War crimes envisaged in the 1949 [Geneva] Conventions … and in the [1977 Additional Protocols I and II] … , as well as in Article 8(2)(f) of the [1998 ICC Statute], and listed below, … constitute crimes under international law and shall be punished in accordance with the provisions of the present title … :
12. intentionally launching an attack in the knowledge that such attack will cause … widespread, long-term and severe damage to the natural environment, which would be excessive in relation to the concrete and direct military advantage anticipated. 
Belgium, Law relating to the Repression of Grave Breaches of International Humanitarian Law, 1993, as amended on 23 April 2003, Article 1 ter, § 1(12).