Règle correspondante
Belgium
Practice Relating to Rule 145. Reprisals
Section C. Proportionality of reprisals
Belgium’s Law of War Manual (1983) states that, when recourse is made to reprisals, the following conditions must be fulfilled: “3) the damage suffered by the adversary must be proportionate to the damage that he has caused”. 
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. 35.
In 1967, a Belgian Senator stated with respect to bombardments of North Vietnam by the United States: “It is recognized today that [reprisals] must be proportionate to the injury suffered. In case one has not suffered any damage, as it was the case, it is incomprehensible to pretend to start a period of bombardments on North Vietnam, as reprisals for attacks on the high sea.” 
Belgium, Parliamentary Debates, 30 November 1967, Annales Parlementaires, Senate, p. 95, reprinted in RBDI, Vol. 6, 1970, pp. 656–657.