It has been claimed that cross-border business transactions are governed by a transnational body of norms specific to international trade, generally known as lex mercatoria, the law merchant. This legal phenomenon is in fact often described as the new lex mercatoria, as distinguished from the ancient law merchant, which purportedly flourished in medieval and early modern Europe. Here, Hatzimihail discusses about lex mercatoria, which has been variously described by its advocates as a set of general principles and customary rules spontaneously referred to or elaborated in the framework of international trade.