Are the roots of the modern Lex Mercatoria really medieval?

This article analyzes how trade was conducted between the tenth and thirteenth centuries. We claim that, as most exchange was simultaneous, differences between law codes did not pose a substantial problem and that mercantile guilds developed not to provide institutions comparable to the modem lex mercatoria, but rather to supply physical security. The development of nonsimultaneous exchange was made possible predominantly by the emergence of urban au- tonomy and urban law applicable to all merchants trading within town, so it appears that the importance of universally accepted commercial institutions in the Middle Ages has hitherto been vastly overrat