Rome Convention
Article 19
States with more than one legal system
1. Where a State comprises several territorial units each of which has its own rules of law in respect of contractual obligations, each territorial unit shall be considered as a country for the purposes of identifying the law applicable under this Convention.
2. A State within which different territorial units have their own rules of law in respect of contractual obligations shall not be bound to apply this Convention to conflicts solely between the laws of such units.