Interaction Between Appreciation Doctrine and International Custom

Customary law is a dynamic source of international law that forms by various act of international players. Applying of margin of appreciation and its invoking is involved the one that can raise its formation as a customary rule. It has been examined in this research whether states invoking on margin of appreciation before any dispute settlement bodies as a defense and its assessment, will be led to its formation as a customary rule or not. For this purpose, requirements needed to identify customary rule, as well as capabilities and challenges that dispute settlement bodies, in particular ECHR, faces with, to stablish customary rules, has been assessed. by distinguishing between the role of states and dispute settlement bodies, the article concludes that Despite of possibility of its formation, there are certain restrictions and ambiguities for recognizing the content of the margin of appreciation as a customary rule, which international law rules has not yet provided any answer to them.