Moral norms are widely thought to have an inescapable authority over us. One of the currently most influential strategies to explain this presumed authority is constitutivism, according to which moral norms can be understood as constitutive rules for activities or practices, such as practical deliberation, which, themselves, are taken to be inescapable for us. The best-known version of this strategy is, arguably, Kantian constitutivism, as developed, eg by Christine Korsgaard. In my talk, I will look at the prospects of a robustly capacity-based version of constitutivism. I will look at different respects in which taking practical and moral norms to emerge from the rational capacities available to us for solving practical problems might have significant advantages over other forms of constitutivism. I will also consider how such an approach relates to the issue of how we should understand moral responsibility. While the general approach of a capacity-based constitutivism has been suggested, eg, as an interpretation of Kant's own views, its systematic potential still merits further exploration, which might open yet another fertile field of application for a realistic understanding of faculties and capacities.