The paper explores Thomas Christiano’s conception of international legitimacy. It argues that his account fails to fully appreciate the instrumental constraints that international legitimacy imposes on national democracies. His model of Fair Voluntary Association articulates the transmission of political legitimacy through a double aggregation of political consent. First, it “pools” its authority from the foundational cosmopolitan claims of individuals involved in a deeply interdependent social world; it then translates this source of legitimacy to international organizations through state consent. However, this model fails to enforce compliance with the cosmopolitan standards and commitments regarding vulnerable populations. The paper argues (i) that the global standards of legitimacy operate as objective criteria of instrumental legitimacy for the reflective evaluation of democratic states, (ii) that the demand of consistent compliance with these cosmopolitan goals imposes external constraints on the institutions of domestic democratic deliberation; and finally, (iii) that if democratic states fail to implement reforms in this direction, then their citizens have the legitimate prerogative to disaggregate their cosmopolitan contribution and direct it to the global institutions that officially realize these goals.