The paper analyses the role of parties’ autonomy in international commercial contracts arguing that (i) the regulation of such contracts is less and less entrusted to the application a single state legal system, (ii) private autonomy operates in favour of the application of substantive rules pursuing the objective of the economic transaction as per the parties’ intention, (iii) as a result, international contractual relationships are subject to a “set of rules” drawn up in accordance with the characteristics of the market in which the relevant relationship is designed to operate; (iv) these rules can be profitably resorted to insofar as are they are “generally accepted in an international, supranational or regional level in tune with the particular needs of international commerce” and do not conflict with public policy or overriding mandatory rules of any States having a legitimate and recognised interest into their application for the benefit of a fair trade.