translate English to French: The according of such discretionary power to either of the contracting States' authorities needs to be examined closely from the standpoint of the principles of reciprocity, pacta sunt servanda and legal certainty, contravened in this case by the wide scope for discretion allowed to either of the two States unilaterally — acting either as source State or residence State — to decide whether to apply the terms of the treaty.
L'attribution d'un tel pouvoir discrétionnaire à l'une ou l'autre partie contractante doit être examiné de près du point de vue de la règle pacta sunt servanda et des principes de réciprocité et de sécurité juridique.