In WTO dispute settlement, the issue about the characterization ofnational law interpretation is concerned with judicial deference and theallocation of power between the WTO and Member States. This articleexamines WTO tribunals' claim about their characterization of nationallaw interpretation and their practice. On the one hand, WTO tribunals haveclaimed to characterize national law interpretation as a question of law; onthe other hand, they have applied the same rule on the burden of proof fornational law interpretation with that for other facts and provided deferenceto the legislating states especially in the circumstances where there is anysuspicion or uncertainty about the meaning of national law. Therefore,WTO tribunals' claim about the characterization is not consistent with theirpractice. WTO tribunals' national law interpretation, in essence, isreinterpretation of national law, and should be characterized as a mixedquestion o flaw and fact.