This chapter assesses R2P's legal cogency within the framework of Habermas' constitutional cosmopolitan approach. It argues that the doctrine is part of the establishment of a "new" hierarchy of law; establishes a clear jurisdictional relationship between the authority of the international community and the authority of sovereigns; and is a novel construct that uses pre-existing legal principles as "building blocks' for a new international order. Furthermore, the chapter articulates that progress under R2P has been evidenced in practice, with the doctrine occupying a space at the high end of the norm cascade spectrum. Consequently, through its locus as a novel and nascent international legal principle, R2P has strengthened the claim that the UN embodies the foundations of a weak yet emerging global constitutional order resembling something analogous to a legally constituted political community of states and citizens, tacitly extending Habermas' constitutional cosmopolitan approach. At the same time, R2P has come to provide a platform for the constitutionalisation and grounding of cosmopolitan ethical norms, engendering a sense of optimism surrounding the evolution towards a more cosmopolitan approach to human protection in the post-Cold War period.