Exploitation of natural resources has become one of the principal means for parties to an armed conflict to finance their armed struggle. In response to this reality, several international approaches have been developed to curtail – what can be referred to as – ‘illegal’ exploitation of natural resources. The current chapter examines how ‘illegality’ is construed in this context and compares this to understandings of illegality within (domestic) peace settlements and the international legal framework for the governance of natural resources. The purpose of this inquiry is to understand how and to what extent international interventions support arrangements for the management of natural resources as set out in peace agreements. The chapter concludes that the international legal framework, international interventions and arrangements in domestic peace settlements are, for the most part, mutually supportive. At the same time, peace settlements tend to take a more expansionist approach of illegality compared to international interventions, including in their definition mismanagement of natural resources or their revenues by governments. Based on these precedents in domestic peace settlements, the chapter argues in favour of recalibrating conceptions of illegality in international approaches.