3. This contribution reports on discussions that took place during an International seminar on comparative labour law in Bordeaux in July 2005, on the topic of the effectiveness of social law. 4. Sur, M. (2006); more generally, for an international, comparative approach to judicial monitoring: (Auvergnon, 2002) 5. Is it possible to deduce that law does not deserve to be effective from the existence of illegal practices or avoidance of the law? 6. Do social norms cost a lot of money? What is the basis for this statement? ILO and OECD reports have recently estimated that, on the contrary, layoffs do not cost very much.