Abstract
The United Nations Convention on the International Sale of Goods(CISG) leaves a number of aspects concerning commercial sales untouched. In particular, it is not concerned with the validity of the contract or of any of its provisions or of any usage. And UNIDROIT don't deal with all-round validity in International Commercial Contract. Especially, UNIDROIT includes declaration of intention department. The UNIDROIT contains the chapter 3 on the "validity" in terms of the defects of consent such as mistake, fraud, and threat as well as "gross disparity". Notwithstanding these provisions, the Principles did not deal with invalidity arising from the lack of capacity or authority, or immorality or illegality. On the other hand, there are arguments that the corresponding provisions of the Principles of International Commercial Contracts(UNIDROIT Principles; PICC). Therefore, Validity in International Commercial Contract is delegate by Each Country Law. So Trade practicer should know full well about Each Country Law Position. People(human, corporation, company) of position Trade practice classify each country civil law relation to validity of commercial contract. This paper is to examine the Validity of UNIDROIT Principles. Also this paper analyses comparison on each country position relation to capacity of right, capacity to act, illegality of contract, declaration of intention. In conclusion, This paper expect that people of trade practice makes use of analysis knowledge.