Taxing multinational enterprises (MNEs) is inherently conflictual because national tax systems are not well designed to handle their international activities. The OECD has been instrumental in developing an international tax regime to govern the conflicts and interdependencies induced by national taxation of MNEs. The strength of this regime depends on the extent to which states adhere to the regime's norms and practices. We examine the OECD's Harmful Tax Competition initiative, arguing that tax havens have been as renegade states in the international tax regime. We explore how the OECD initiative developed and evaluate its impact on regime effectiveness.