Competing methods and norms in the regulation of international sales

The study explores the unification of private international law and substantive contract law in the field of international sales law. It starts by asking whether the instruments of uniform substantive contract law can fully replace the rules of private international law, as well as if different periods be distinguished: can it be said that, at first, private international law played the decisive role in the settlement of international commercial disputes, followed by the law of traders, the Lex Mercatoria, and then by uniform norms of substantive law? Or is the relationship more sophisticated, because different gates open between the instruments of substantive law and conflict of laws? Can private international law eventually play a role in determining the application of substantive law conventions or in filling gaps in the uniform law? In the second part of the paper, several examples demonstrate that the unification of substantive law and private international law does not exclude or make each other superfluous; they live in a multifaceted relationship, besides competing as part of their long-lasting coexistence.