Abstract This chapter weighs the pros and cons of applying the insights of constitutionalism to issues of global law. After sketching the challenge both global constitutionalism and global administrative law face in the precarious legitimacy of transnational and global governance, it examines more closely the scope and aims of both projects. It is in their respective ambitions that the key difference between the two lies: constitutionalist visions set out to describe and develop a fully justified global order, while global administrative law approaches are more limited in scope, focusing on particular elements of global governance and confining themselves to the analysis and realisation of narrower political ideals, especially accountability. Such a limited approach does, however, raise serious problems, both on the practical and the normative level. The chapter focuses on only on two sets of issues: the difficulty in separating ‘administrative’ from ‘constitutional’ issues, and the risk of legitimising illegitimate institutions, in part by elevating them to the level of law. Although the resulting challenge for global administrative law is serious and will condition the further trajectory of the project, it should not distract from the significant advantages its more limited ambition entails.