States have long claimed the power to ‘self-judge’ the interpretation and application of norms of international law that relate to particularly sensitive issues, such as national security. However, allowing for legally binding unilateral decision-making creates the risk of abuse by states and is thus denounced by most international lawyers. Increasing arguments of self-judgment in practice disclose a need to conceptualise the phenomenon and its limits coherently. The only way to do so is by studying the evolution and functions of self-judgment, as well as the tensions that underpin it.

Against the backdrop of its intellectual history, this thesis conceptualises self-judgment as the authoritative application of international legal norms. It uncovers self-judgment as the site of persistent contestation, caught between judicialisation and pushback. Based on an extensive study of self-judgment in treaty practice and a cross-institutional analysis of the case law of international judicial bodies, the thesis unravels this process of contestation in four stages. First, in line with evolving conceptions of sovereignty throughout the 20th century international judicial bodies were instrumental in articulating a presumption against self-judgment. Following this, states shifted to ever more explicit language in a second stage, aiming to safeguard their self-judgment authority in legal instruments. Third, international judicial bodies have been relying on ‘good faith review’ as a potent tool to limit self-judgment by ‘judicialising’ it. Fourth, an emerging trend of reinforced self-judgment in treaty-making reveals how some states have resisted the judicialisation process, insisting on their right to authoritatively determine how the law applies in certain cases.

In addition to uncovering this dialectic of self-judgment, the thesis also analyses the key factors in this process of contestation. It reveals the risks that self-judgment provisions can pose by facilitating abuse by states and threatening the normativity of treaty frameworks and considers the value of good faith review to manage those risks. At the same time, it argues that international judicial bodies must apply good faith review deferentially in ways that allow self-judgment provisions to fulfil their functions. Otherwise, practices such as reinforced self-judgment, an effective tool to roll back judicialisation, may continue to proliferate.