Party autonomy is a principle relating to the freedom of the parties to choose the law applicable to an international contract. However, this principle is limited by rules of public policy, and more generally by mandatory provisions, which reduce the scope of this autonomy. In order to improve the application of these rules while guaranteeing a degree of predictability, it is important to study in detail the origin and nature of public policy rules. A comparative study with Egyptian private international law is necessary to perfect the current mechanisms. The current conceptual debate highlights the role of international cooperation, in addition to purely state interests, which will give rise to a new transnational, even supranational, public policy.