Global constitutionalism is an agenda that identifies and advocates for the application of constitutionalist principles in the international legal sphere. Global constitutionalization is the gradual emergence of constitutionalist features in international law. Critics of global constitutionalism doubt the empirical reality of constitutionalization, call into question the analytic value of constitutionalism as an academic approach, and fear that the discourse is normatively dangerous because it is anti-pluralist, artificially creates a false legitimacy, and promises an unrealistic end of politics. This article addresses these objections. I argue that global constitutionalization is likely to compensate for globalization-induced constitutionalist deficits on the national level, that a constitutionalist reading of international law can serve as a hermeneutic device, and that the constitutionalist vocabulary uncovers legitimacy deficits of international law and suggests remedies. Global constitutionalism, therefore, has a responsibilizing and much-needed critical potential.