The purpose of the PhD research project is to develop a comparative study of the normative power of social partners in Luxembourg, France and Germany. The main research question is the role of the law in the development of this normative power. Indeed law plays two different roles regarding collective agreements. We may consider law as an “organizer” of the normative power of social partners, providing a legal framework for collective bargaining and collective agreements. Law may alternatively constitute a “rival norm” of collective agreements, as law and collective agreement are two different sources of labour law.In this research project I will tackle four different issues related to the role of the law in the development of the normative power of social partners. The first issue deals with the origins of this normative power: what is the role of the law in the emergence of collective agreements? The second issue deals with the actors (social partners): who has the possibility to negotiate collective agreements? What are the legal conditions, which allowed an organization of employees or employers the ability to negotiate a collective agreement? The third issue deals with the legal framework of the collective bargaining (such as the obligation to negotiate) and the legal framework of the collective agreement: what is the possible content of a collective agreement, what is the scope of the normative power of social partners? Fourthly, I we will study the question of the “normative force” of such agreements having regards to the law and how these two norms coexist. This PhD project therefore intends to provide a better understanding of normative power of social partners in the Luxembourg’s law through the prism of German and French laws.