In his work, Jules Coleman has held that the rule of recognition, if conceived of as a shared cooperative activity, should be the gateway through which to incorporate moral constraints on the content of law. This analysis, however, leaves unanswered two important questions. For one thing, we do not know when or even why morality becomes a criterion of legality. And, for another thing, we still do not know what conception of morality it is that we are dealing with. In this article, we will attempt to clarify in greater depth what relations there are between the social practice of law and morality. We will thus see how the cooperative nature of social practices imbues law with a moral force, and how this makes it possible to establish a "weak" connection between law and morality: To see this, we will need to single out some basic features of cooperative social practices, thus setting out a suitable framework for the view just mentioned.