Related Rule
Belgium
Practice Relating to Rule 100. Fair Trial Guarantees
Belgium’s Law of War Manual (1983) refers to common Article 3 of the 1949 Geneva Conventions and prohibits the conviction of protected persons without a prior fair trial. 
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. 17.
The manual further states that depriving a prisoner of war or other protected persons of the right to be tried by a regular court is a grave breach of the 1949 Geneva Conventions. 
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 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 … :
8. depriving a prisoner of war, a civilian protected by the [1949 Geneva] Convention [IV] on the protection of civilians in times of armed conflict, or a person protected by [the 1977] Additional Protocols I and II to the … 1949 Geneva Conventions of his right to a fair and regular trial under the provisions of those instruments. 
Belgium, Penal Code, 1867, as amended on 5 August 2003, Chapter III, Title I bis, Article 136 quater, § 1(8).
Belgium’s Law concerning the Repression of Grave Breaches of the Geneva Conventions and their Additional Protocols (1993), as amended in 1999, provides that “denying a prisoner of war [or] a protected civilian person the right to a fair and impartial trial” 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)(5).
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 … :
5. depriving a prisoner of war, a civilian protected by the [1949 Geneva] Convention [IV] on the protection of civilians in times of armed conflict, or a person protected by [the 1977] Additional Protocols I and II to the … 1949 Geneva Conventions of his right to a fair and regular trial under the provisions of those instruments. 
Belgium, Law relating to the Repression of Grave Breaches of International Humanitarian Law, 1993, as amended on 23 April 2003, Article 1 ter, § 1(5).
At the CDDH, Belgium stated that the guarantees contained in Article 6 of the 1977 Additional Protocol II were based on customary international law and human rights law. 
Belgium, Statement at the CDDH, Official Records, Vol. VIII, CDDH/I/SR.33, 19 March 1975, p. 323, § 41.
Belgium’s Law of War Manual (1983) provides that depriving a prisoner of war or other protected persons of the right to be judged by an impartial court is a grave breach of the 1949 Geneva Conventions. 
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 Penal Code (1867), as amended in 2003, provides:
In the case of an armed conflict as defined in … Article 3 common [to the (1949) Geneva Conventions], the grave breaches of [common] Article 3, … listed below, shall constitute crimes under international law and shall be punished in accordance with the provisions of the present title, when such breaches endanger, by act or omission, persons protected by these Conventions, without prejudice to criminal provisions applicable to breaches committed out of negligence:
4. the passing of sentences and the carrying out of executions without previous judgment pronounced by a regularly constituted court, affording the judicial guarantees which are generally recognized as indispensable. 
Belgium, Penal Code, 1867, as amended on 5 August 2003, Chapter III, Title I bis, Article 136 quater, § 2(4).
Belgium’s Law relating to the Repression of Grave Breaches of International Humanitarian Law (1993), as amended in 2003, provides:
In the case of an armed conflict as defined in … Article 3 common [to the (1949) Geneva Conventions], the grave breaches of [common] Article 3, … listed below, shall constitute crimes under international law and shall be punished in accordance with the provisions of the present title, when such breaches endanger, by act or omission, persons protected by these Conventions, without prejudice to criminal provisions applicable to breaches committed out of negligence:
4. the passing of sentences and the carrying out of executions without previous judgment pronounced by a regularly constituted court, affording the judicial guarantees which are generally recognized as indispensable. 
Belgium, Law relating to the Repression of Grave Breaches of International Humanitarian Law, 1993, as amended on 23 April 2003, Article 1 ter, § 2(4).