This book provides an in-depth analysis of EU-Tunisia negotiations during the last three decades to understand what 'joint ownership' means in Euro-Mediterranean relations. The principle of joint ownership often figures in the EU's public discourse of the EU and other international actors. Yet, it has been scarcely conceptualised and there is little research on which factors determine its presence or lack thereof. The book contributes to its definition, highlighting its evolving nature and intersubjective dimension. The author further explains how bargaining rules, practices, and procedures affect joint ownership by constraining or empowering actors, and shaping their expectations about which options they perceive are possible during the negotiations. Negotiation analysis proves useful for showing how, and to what extent, the interests of both sides eventually feature in Euro-Mediterranean agreements and enables scholars to bring back third countries' agency and perceptions into the study of the EU's external relations.