Related Rule
Belgium
Practice Relating to Rule 50. Destruction and Seizure of Property of an Adversary
Belgium’s Law of War Manual (1983) provides that “extensive destruction or appropriation of property not justified by military necessity and carried out unlawfully and wantonly” is a grave breach of the 1949 Geneva Conventions and a war crime. 
Belgium, Droit Pénal et Disciplinaire Militaire et Droit de la Guerre, Deuxième Partie, Droit de la Guerre, Ecole Royale Militaire, par J. Maes, Chargé de cours, Avocat-général près la Cour Militaire, D/1983/1187/029, 1983, p. 55.
Belgium’s Teaching Manual for Soldiers states: “Civilian property is, in principle, not to be destroyed except as strictly necessary to the execution of the mission.” 
Belgium, Droit de la Guerre, Dossier d’Instruction pour Soldat, à l’attention des officiers instructeurs, JS3, Etat-Major Général, Forces Armées belges, undated, p. 7; see also p. 21.
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 … :
12. destroying or seizing the enemy’s property, in case of international armed conflicts, or an adversary’s property, in case of armed conflicts non-international in nature, unless such destruction or seizure be imperatively demanded by the necessities of war;
13. extensive destruction and appropriation of property, not justified by military necessity as admitted by international law and carried out unlawfully and wantonly. 
Belgium, Penal Code, 1867, as amended on 5 August 2003, Chapter III, Title I bis, Article 136 quater, § 1(12)–(13).
Belgium’s Law concerning the Repression of Grave Breaches of the Geneva Conventions and their Additional Protocols (1993), as amended in 1999, provides that “extensive destruction and appropriation of property not justified by military necessity as permitted by international law and carried out unlawfully and wantonly” constitutes a crime under international law. 
Belgium, Law concerning the Repression of Grave Breaches of the Geneva Conventions and their Additional Protocols, 1993, as amended in 1999, Article 1(3)(8).
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 … :
7 bis destroying or seizing the enemy’s property, in case of international armed conflicts, or an adversary’s property, in case of armed conflicts non-international in nature, unless such destruction or seizure be imperatively demanded by the necessities of war;
8. extensive destruction and appropriation of property, not justified by military necessity as admitted by international law and carried out unlawfully and wantonly. 
Belgium, Law relating to the Repression of Grave Breaches of International Humanitarian Law, 1993, as amended on 23 April 2003, Article 1 ter, § 1(7 bis)–(8).