Traditionally, conflict of law rules designate only national substantive law as the applicable law. Many unifying and harmonizing substantive law instruments of both States and non-State organizations, however, are designed specifically for application to cross-border relationships. Achieving this objective is, generally, hindered by conflict of law rules. The requirements which non-national law needs to fulfil in order to be accepted as the law governing a cross-border relationship deserve clarification. Not only uniform law, such as the CISG and the envisaged European substantive law...