Transition from armed conflict to peace is a matter largely governed by international law, both in international and non-international armed conflicts. However, the legal regulation applicable to transition to peace is not gathered into a unified body of law, but provisions belonging to different branches of international law can apply, interacting among them and with domestic law. To offer an analytical framework on this interaction, academic scholarship has proposed the concept of jus post bellum, which despite a long tradition as a moral category within the just war theory only entered the legal scholarship since 2005. Up to now, studies on the matter have been focused on the theoretical foundation of the concept and its application to international armed conflicts. Having such a background, the recent Colombian peace process and its 2016 peace agreement offer a suitable case study to analyse both the role of international law in transition to peace and the value of jus post bellum to frame such a role in a non-international armed conflict. It is due to the comprehensiveness of the Colombian process ending armed conflict and addressing its root causes, as for its explicit commitment to international legal standards. The thesis analyses how the theoretical development of jus post bellum is reflected in practice, and how practice offers new insights to keep developing the concept as the normative framework for transition from armed conflict to peace. New elements are identified through the case study, assessing the concrete content and functioning of jus post bellum and discussing the challenges and opportunities of bringing the concept from theory to practice.