  Explaining the rationale of legal authority, however, is not the only component of a theory about the normativity of law. If we hold the legal positivist thesis that law is essentially founded on social conventions, another important question arises here: how can a conventional practice give rise to reasons for action and, in particular, to obligations? Some legal philosophers claimed that conventional rules cannot, by themselves, give rise to obligations. As Leslie Green observed, Hart’s “view that the fundamental rules [of recognition] are ‘mere conventions’ continues to sit uneasily with any notion of obligation,” and this Green finds troubling, because the rules of recognition point to the “sources that judges are legally bound to apply” (Green 1996, 1697). The debate here is partly about the conventional nature of the rules of recognition, and partly about the ways in which conventions can figure in our reasons for action. According to one influential theory, inspired by David Lewis (1969) conventional rules emerge as solutions to large-scale and recurrent coordination problems. If the rules of recognition are, indeed, of such a coordination kind, it is relatively easy to explain how they may give rise to obligations. Coordination conventions would be obligatory if the norm subjects have an obligation to solve the coordination problem which initially gave rise to the emergence of the relevant convention. It is doubtful, however, that the conventions at the foundations of law are of a coordinative kind. In certain respects the law may be more like a structured game, or an artistic genre, which are actually constituted by social conventions. Such constitutive conventions are not explicable as solutions to some pre-existing recurrent coordination problem. The conventional rules constituting the game of chess, for example, are not there to solve a coordination problem between potential players. Antecedent to the game of chess, there was no particular coordination problem to solve. The conventional rules of chess constitute the game itself as a kind of social activity people would find worthwhile engaging in. The constitutive conventions partly constitute the values inherent in the emergent social practice. Such values, however, are only there for those who care to see them. Constitutive conventions, by themselves, cannot ground an obligation to engage in the practice they constitute.