Règle correspondante
Practice relating to Rule 66. Non-Hostile Contacts between the Parties to the Conflict
Section D. Refusal to receive parlementaires
Belgium’s Law of War Manual (1983) provides: “The chief to whom a parlementaire is sent is not obliged to receive him in all circumstances.” It also states that it is prohibited for commanders to decide a priori that they will not receive parlementaires. 
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. 40.
Belgium’s Teaching Manual for Officers (1994) states that the parlementaire “does not necessarily have to be received by the adverse party”. 
Belgium, Droit de la Guerre, Manuel d’Instruction pour Officiers, Etat-Major Général, Division Opérations, 1994, Part I, Title II, p. 25.