Peace-making to end an internal armed conflict often requires constitutional change. When such change takes place within an existing constitutional framework, unconstitutionality challenges can arise as the implementation of a peace agreement may require departures from existing constitutional provisions. This tension raises the issue of whether the requirements of peace-making and constitutional principles can be reconciled without risking the achievement of peace or the constitutionality of the constitutional order. This paper develops a theoretical framework within which this reconciliation can be accommodated, by conceptualising peace as the absence of violence and as an aspect of the rule of law. Drawing on Fuller’s distinction between the moralities of duty and aspiration, it then presents achieving peace as a constitutional duty and achieving the rule of law as a constitutional aspiration.