Related Rule
Belgium
Practice Relating to Rule 155. Defence of Superior Orders
Belgium’s Penal Code (1867), as amended in 2003, provides:
The fact that the accused has acted pursuant to the order of his government or of a superior does not exempt him from his responsibility if, under the given circumstances, the order could have clearly led to the commission of one of the offences set forth in Articles 136 bis, 136 ter, and 136 quater [grave breaches of IHL]. 
Belgium, Penal Code, 1867, as amended on 5 August 2003, Chapter III, Title I bis, Article 136 octies, § 2.
Belgium’s Law concerning the Repression of Grave Breaches of the Geneva Conventions and their Additional Protocols (1993), as amended in 1999, provides:
The fact that the defendant acted on the order of his/her government or a superior shall not absolve him/her from responsibility where, in the prevailing circumstances, the order could clearly result in the commission of a crime of genocide or of a crime against humanity … or a grave breach of the Geneva Conventions … and their Additional Protocol I. 
Belgium, Law concerning the Repression of Grave Breaches of the Geneva Conventions and their Additional Protocols, 1993, as amended in 1999, Article 5(2).
In the Sergeant W. case in 1966, Belgium’s Court-Martial of Brussels sentenced a sub-officer to three years’ imprisonment for the wilful killing of a civilian. The accused, who at the time of the event was chasing rebels, was serving in the Congolese army within the framework of military technical co-operation between Congo (Democratic Republic of the Congo) and Belgium. He invoked the defence of superior orders. The Court held that, the accused’s interpretation of the order he had received, i.e. to kill an unarmed person in his power, was manifestly unlawful; the accused therefore had a duty to disobey this order. 
Belgium, Court-Martial of Brussels, Sergeant W. case, Judgment, 18 May 1966.
In its judgment in the V.C. case in 1983, in which the accused, a mercenary in Katanga (Congo/Democratic Republic of the Congo), was ordered to kill a wounded person, Belgium’s Court of Cassation held that there was no general principle of law that allowed the killing of a wounded person because he was “mortally wounded”. An order to kill a wounded person for that sole reason was manifestly criminal. Consequently, the justification of a superior’s order could not be raised. 
Belgium, Court of Cassation (Second Chamber), V.C. case, Judgment, 12 January 1983.
In its judgment in the Kalid case in 1995, a Belgian Military Court, with respect to the requirements for relying on a superior’s order as grounds for justification, stated that in accordance with domestic and international law, to be able to claim a superior’s order as grounds for justification:
(a) the cited order must be given beforehand, and its implementation must correspond to the purpose of that order,
(b) the cited order must be issued by a legitimate superior acting within the limits of his authority,
(c) the order issued must be legitimate, i.e., in conformity with the law and regulations;
… in connection with this last point, it may generally be assumed that a soldier of the lowest rank may base his actions on the assumption that the order was legitimate. 
Belgium, Military Court, Kalid case, Judgment, 24 May 1995.
In an explanatory memorandum submitted to the Belgian Senate in the context of the adoption of the Law concerning the Repression of Grave Breaches of the Geneva Conventions and their Additional Protocols in 1991, which excludes the defence of superior orders in cases “where, in the prevailing circumstances, the order could clearly result in the commission of a crime of genocide or of a crime against humanity … or a grave breach of the Geneva Conventions … and their Additional Protocol I”, it is stated that the words “if he had the option of not obeying” were omitted since this would necessarily be deduced from general principles of penal law regarding compulsion. 
Belgium, Senate, Explanatory Memorandum, Draft Law concerning the Repression of Grave Breaches of the Geneva Conventions and their Additional Protocols, 1990–1991 Session, Doc. 1317-1, 30 April 1991, p. 15.