Related Rule
Belgium
Practice Relating to Rule 71. Weapons That Are by Nature Indiscriminate
According to Belgium’s Teaching Manual for Officers (1994), it is especially forbidden to use indiscriminate weapons. 
Belgium, Droit de la Guerre, Manuel d’Instruction pour Officiers, Etat-Major Général, Division Opérations, 1994, p. 36, § 17.
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 … :
40. employing weapons, projectiles, material and methods of … which are inherently indiscriminate in violation of the international law of armed conflict, provided that such weapons, projectiles, material and methods of warfare are the subject of a comprehensive prohibition and are included in an annex to the Statute of the International Criminal Court. 
Belgium, Penal Code, 1867, as amended on 5 August 2003, Chapter III, Title I bis, Article 136 quater, § 1(40).
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 … :
26. employing weapons, projectiles, material and methods of … which are inherently indiscriminate in violation of the international law of armed conflict, provided that such weapons, projectiles, material and methods of warfare are the subject of a comprehensive prohibition and are included in an annex to the Statute of the International Criminal Court. 
Belgium, Law relating to the Repression of Grave Breaches of International Humanitarian Law, 1993, as amended on 23 April 2003, Article 1 ter, § 1(26).