The EU plays a high-profile role in the international arena, and yet this role still evades accurate conceptualization. Since the EU is not a state, it is commonly accepted as sui generis; a normative power influencing the world order mostly by means of direct and intermediary persuasion. Despite this position, in practice when championing the global normative agenda, the EU does not always demonstrate high efficiency as a leader. This article studies the EU’s efforts to push through regional and global versions of a financial transaction tax, meant to promote the common good through the positive externalities it generates for the economy. The aim of the article is to arrive at an adequate explanation for the (in)ability of the EU to act as an agent of global governance in this case. The focus of attention is the inner organizational limitations on the EU’s behaviour as a global actor.