English to French Social Sciences International Org/Dev/Coop Trade negotiations

...elimination of discriminatory treatment in international relations” as an objective of the xxx trade system and stated that the most favoured nation's commitment taken by YYY (int. org) Members is a fundamental instrument for achieving that aim. Therefore, when establishing a trade agreement, either a YYY (int. org) Member will need some kind of ***derogation*** to avoid legal inconsistency with the most favoured nation's rule or it could seek a waiver. However, through a time, the system itself has developed conditional exceptions which a member could invoke....

PS: My problem is, since "waiver" means "derogation", I need to find another word in French for "derogation".
Difficile d'en trouver jusqu'a l'heure
Merci d'avance