Related Rule
Belgium
Practice Relating to Rule 62. Improper Use of Flags or Military Emblems, Insignia or Uniforms of the Adversary
Belgium’s Law of War Manual (1983) provides:
The [1907 Hague Regulations] prohibits to use “improperly” the national flag, or the military insignia and uniform of the enemy.
The word “improperly” must be stressed. It follows that opening fire or participating in an attack while wearing the enemy uniform doubtlessly constitutes an act of perfidy. It is also the case when opening fire from a captured enemy combat vehicle with its insignia.
However, infiltrating enemy lines in order to create panic to the point that the adversary starts firing on its own soldiers believing that they are disguised enemies or operating behind enemy lines wearing enemy uniform in order to collect information or commit acts of sabotage is not considered as using “improperly” enemy uniform …
It is a recognized practice that warships may, without contravening the law of war, fly the enemy flag, as a ruse, on the condition that at the moment of opening fire the warship shows her true colours …
It is prohibited for belligerents to display false markings, especially enemy markings, on their military aircraft. 
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, pp. 32 and 33.
[emphasis in original]
Belgium’s Teaching Manual for Officers (1994) provides: “The use of flags, symbols, insignia and uniforms of the enemy is prohibited during attacks or to shield, favour, protect or impede a military operation.” 
Belgium, Droit de la Guerre, Manuel d’Instruction pour Officiers, Etat-Major Général, Division Opérations, 1994, Part I, Title II, p. 34.
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 … :
30. improper use of … the flag or the military insignia and uniform of the enemy … , when it results in loss of life or serious injury. 
Belgium, Penal Code, 1867, as amended on 5 August 2003, Chapter III, Title I bis, Article 136 quater, § 1(30).
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 … :
16 bis improper use of … the flag or the military insignia and uniform of the enemy … , when it results in loss of life or serious injury. 
Belgium, Law relating to the Repression of Grave Breaches of International Humanitarian Law, 1993, as amended on 23 April 2003, Article 1 ter, § 1(16 bis).