Self-determination and sovereignty-based conflicts are widespread throughout the globe, and are particularly durable and deadly.These conflicts may be resolved through military victory, through some form of enhanced internal self-determination, or through a path to external self-determination. This chapter explores the puzzle of whether and how to provide for external self-determination as a means for ensuring a durable peace. This chapter reviews the peace processes related to conflicts in Bosnia, Indonesia/East Timor, Israel/Palestine, Kosovo, Northern Ireland, Papua New Guinea/Bougainville, Serbia/Montenegro, Sudan/South Sudan, and Western Sahara in order to understand how the parties seek to most effectively share sovereignty in the interim; build sustainable institutions; determine final status; phase in the assumption of sovereignty; condition the assumption of this newfound sovereignty; and, if necessary, to constrain the exercise of sovereignty of the new state.

This chapter develops a history of internal self-determination. It shows that internal self-determination, as an idea, has a long history; and that the internal dimension of self-determination has always been an essential part of the broader concept of self-determination. The chapter also argues that the construction of the internal–external dichotomy took place in the 1940s due to the intervention of the Netherlands, in the context of Indonesia's decolonization. The principle started to become popular during the Cold War. The Cold War's end resulted in a renewed interest in self-determination, with international lawyers starting to write about it. This history is critically narrated in this chapter.