The rights-based approach (RBA) to development is now accepted practice among experts in the United Nations (UN) development machinery, as well as key bilateral aid agencies and many nongovernmental organizations (NGOs). That development should be informed by rights represents a new human rights norm in world affairs, and the machinery around it forms a regime. However, RBA remains contested, and implementation has been stuttering and incomplete. This article examines the forces working against, and for, the implementation of RBA. It argues, in particular, that although RBA is a norm well institutionalized as a regime, it is not nearly as accepted by states themselves, and thus remains only imperfectly implemented. This, in turn, shows us how various factors affecting norm acceptance-state interests, transnational NGOs, and multilateral actors, among others-interact in norm evolution. The gap between a strong regime and a weak norm helps give insight into the future of RBA: It seems robust due to its institutionalization, but it is much more tenuous than it appears. This can also have implications in other similar situations, such as responsibility to protect or climate change, in which strong regimes belie the weakness of the underlying norm. The rights-based approach to development (RBA) to development is now accepted practice among experts in the UN development machinery, as well as key bilateral aid agencies and many nongovernmental organizations (