‘The different sets of ideas at the back of our heads’: Dissent and authority at the International Court of Justice

© 2019 Foundation of the Leiden Journal of International Law. Additional opinions (AOs) - dissenting opinions, separate opinions and declarations, whether authored individually or jointly - are a distinctive characteristic of the ICJ's jurisprudence. Few decisions of the International Court of Justice (the Court, ICJ) are delivered without any additional opinion attached to it. Yet, despite their ubiquity, there is still significant disagreement as to their relationship to the authority of the Court and its decisions. Although this disagreement is commonly attributed to the different approaches and attitudes traditionally associated with the 'civil law' and 'common law' traditions, few ask specifically why those traditions take the approach they do, and even fewer consider the appropriateness of the extension of those attitudes to the ICJ, which of course is neither 'civil law' nor 'common law'. In this article, using the work of Mirjan Damaška, I offer a contextually coherent and contextually contingent understand of the theory and practice of additional opinions at the ICJ upon which engagement with this practice - by judges, scholars and practitioners - can be premised. This effort to understand the relationship between additional opinions and institutional authority will, by its very nature, lead to a broader enquiry into the very nature of institutional authority at the ICJ. Having explained the importance of AOs to the structural integrity of the Court's authority, I will close this article by highlighting the role of various stakeholders when engaging with that practice to ensure that their institutional function is discharged