Abstract.The concept of co‐ordination problems helps solve the problem of authority and obligation in legal theory, but only if the concept is carefully distinguished from the game‐theoretical concept of co‐ordination problems and their solutions. After explaining the game‐theoretical concept, the author defends its application to legal theory by reviewing the exchange he has had with Joseph Raz about the authority of law. Extending that debate, he argues that criticisms from Raz and others miss the point of the co‐ordination thesis; its primary benefit is that it illuminates the source of law's moral authority in the way law enables individuals to co‐ordinate their actions for the common good without imposing a national common enterpris