Games have usually been taken as offering a good analogy for the analysis of legal concepts. Indeed, it has been argued (though admitedly from a rather different perspective) that this is not only a useful analogy, but that the law is in some sense, essentially similar to games. Among many other authors, as we shall see, Herbert Hart seems to have shared this view and, in The Concept of Law, relied heavily on the similarities between them. In fact, he realied upon that analogy so heavily that it is certainly not too big an exaggeration to say, with Judith Shklar, that games were "Hart's obsession". In what follows I want to focus upon the differences between games and the law. As I hope to show, a clear account of those differences is important not only because the game-analogy has been used so repeatedly in the tradition of analytic jurisprudence, but also because it is the difference between two models of institution that seems to have been overlooked. This distinction is developed as an improvement to John Searle's distinction between regulative and constitutive rules, and it is then used to explain important differences between the law as we know it and ancient Roman and biblical law.