This thesis purports to analyze and criticize the superseding of mandatory rules (provisions) and public order (public policy) over the choice of applicable law in international commercial contracts, regarding the legal framework and case-law in the United States of America (US) and in Europe (European Union). In addition, it aims to determine to what extent mandatory rules and public order, both in the European (European Union) and United States legal framework limit the implementation of the choice of the applicable law in international commercial contracts. It aims to describe the reasons which underpin the prevalence and preference of contractual parties as to stipulating the applicable law in international commercial contracts, instead of applying the default conflict method. It attempts to substantiate the reasons which underpin the prevalence and preference of contractual parties as to stipulating the applicable law in international commercial contracts, instead of applying the default conflict method. It intends to construct a general theoretical conceptualization of the party autonomy principle on choice of law in international commercial contracts, under the lens of Private International Law, as well as illustrating how the aforementioned principle has been regulated in Uniform Law, in the European (European Union) an in the US legal framework. It purports to draw a general theoretical conceptualization of mandatory rules and public policy (public order) on choice of law in international commercial contracts, under the lens of Private International Law. US legal framework refers to the Uniform Commercial Code and the Restatement (Second) of Conflict of Laws and the European legal framework refers to the Rome I Regulation. Finally, it summarizes these limitations in the European and US legal framework as well as providing further explanation of them by presenting and criticizing judicial decisions which have interpreted the practical applicability of mandatory rules and public policy.