The majority of the world ‘ s peoples do not participate in global decision-making regarding who should tax, where, and what. They are excluded mainly because the international tax game is controlled by powerful players that jealously safeguard their outsized, privileged positions. The dominance of a few influential actors over the rest of the world brings into question the political legitimacy of the socalled ‘ international tax regime ‘, through which the global tax base and the world's resources are unevenly shared. Yet even when experts acknowledge the unjust impacts of this regime, their proposed reforms are all too often more top-down solutions without any input from those most adversely affected. These responses tend to overlook the existence of power relations and the plurality of fiscal and economic interests at play, focusing on outputs and disregarding the fact that the underlying problems in international taxation lay squarely on the failure to reach consensual agreement among nations. This chapter argues instead that a just world tax order requires a bottom-up approach, grounded on fundamental principles of legitimacy. By applying democratic and critical legal theory to the current practices of global tax governance, it offers a new way to think politically about fiscal relations among nation-states, and international tax law and policy.