According to the Geneva Unified Law concerning the commercial papers (bill of exchange – promissory note – and cheque) and domestic trade legislations which have quoted provisions of this law, the capacity of a person to bind himself by the commercial papers shall be determined by his national law. But the difference of nationality rules from one country to another in gaining nationality, losing it, retrieving it, and resolutions to be followed in conflicts of nationality, lead, on the international level to the situation of multiplicity of nationalities of people, people without any nationality. Also person's right to change his nationality which is considered a matter of human rights, represents the problem of change in the national law that regulates the legal relation, and the foreigner with incomplete capacity might use many pulative ways to hide his lack of capacity to make the other think he has full capacity. These situations are the problems facing the application of national law on the capacity of the commercial obligation.