In the past two decades or so, an enormous amount of academic international law and policy attention has gone to the concept of jus post bellum, or "post conflict justice." There are various ways of rendering the phrase with varying intellectual or political commitments implied - "post-conflict transitional justice," "law and obligations applicable to the post-conflict," or "moral obligations of parties to a conflict after the conflict," and so on. However exactly one frames it, however, it is increasingly seen by many in the international community as an essential component and complement to the traditional categories of jus ad bellum (the just or lawful resort to force) and jus in bello (the just or lawful conduct of hostilities). The concept in contemporary intellectual discussion traces back, interestingly, not to international law - even academic international law - but instead to just war ethics qua ethics and political science, only later entering into vigorous discussion within academic international law.
As policy in the real world, the concept has been invoked as part of the "package" that gives legitimacy to post-conflict reconstruction efforts and aid, various forms of peacekeeping post-conflict operations, and the 2005 UN decision to create an intergovernmental UN Peacebuilding Commission to support post-conflict missions. As a practical matter, there is broad support for many forms of post-conflict efforts to safeguard a sometimes fragile peace, maintain basic civic security and order in an often chaotic environment, help supervise and act as a neutral guarantor for political transitions, and so on. As I explain in my 2012 book on US-UN relations, Living With the UN: American Responsibilities and International Order (first three chapters available as free pdf here at SSRN), despite all the many problems with such things as sexual abuse or theft of supplies by UN peacekeeping troops, on balance the efforts in peacekeeping and post-conflict order have been one of the relatively few bright spots at the UN over the past dozen years.
Despite these areas of policy and political convergence on the idea of taking account of the needs of the post-conflict, as a matter of legal or moral obligation, jus post bellum raises important philosophical questions, particularly on whether the way in which certain main strands of justification might lead to a collapse of the legally generally regarded as independent categories of jus ad bellum and jus in bello. A new book chapter, in working paper form at SSRN, "The Concept of Jus Post Bellum in International Law: A Normative Critique," by Eric Eric De Brabandere of the Grotius Center at Leiden University School of Law (forthcoming, Carsten Stahn, Jennifer S. Easterday, and Jens Iverson (eds.), Jus Post Bellum: Mapping the Normative Foundations, OUP 2014), gives a conceptual critique. It is of interest not just for the critique - which I find quite powerful, though I won't say I've considered its implications long enough to endorse - but also for the well-organized framing of the historical, political, and philosophical background to jus post bellum. As to the critique, it is provocative and, in my view, important; consider these paragraphs from the discussion of the (possible) relationship of jus post bellum and 'just wars':
Under current international law, the laws relating to armed force are separated into the legality of the use of armed force (jus ad bellum), and the law applicable during an armed conflict (jus in bello), including the laws relating to the occupation of territory by a foreign presence. These two areas of international law are rightly unconnected, in the sense that the violation by a state of its obligations under one system does not by itself amount to a violation of the laws of the other. Similarly, the application of the jus in bello does not depend on the (il)legality of the military intervention. Adding a ‘third’ branch to this dualist regulation of the use of armed force is not as such problematic, were it not that such theories imply that the outcome or result of an armed conflict cannot be detached from the very reasons or legality of the resort to force.
[Brian] Orend notes for example that, ‘the raw fact of victory does not of itself confer rights upon the victor, nor duties upon the vanquished. Might does not equal right. It is only when the victorious regime has fought a just war that we can meaningfully speak of rights and duties of victor and vanquished at the conclusion of armed conflict’. This intrinsic link with the justness of an armed conflict is the inherent flaw and one of the most fundamental problems of this conception of jus post bellum. In times where international law is moving from a jus ad bellum to a jus contra bellum, it seems even more imprudent to assess the legality of an armed conflict in function of its effects, or to grant certain post-conflict responsibilities and rights to states in function of the ‘justness’ of their cause. Moreover, in such case, jus post bellum is as a legal concept is more susceptible to manipulation and to being used as a legitimation, through law, of State specific agendas ....
The only case in which a close link between jus ad bellum and jus in bello can be defended, without resorting to the justification of the use of force in function of the potential positive results of the intervention, is when the use of force has been authorised by the Security Council on humanitarian or related grounds. In that limited case, however, the post-conflict activity should not necessarily be directly linked to the use of force. As said earlier, practice has shown that the Security Council’s activity in this field is independent from any enquiry on the legality of the use of force.
(Abstract below the fold.)
Abstract: This chapter examines the usefulness and accuracy of jus post bellum as a legal concept. It argues that the concept presents a challenge to the objectivity of the post-conflict phase by linking the rights and obligations of foreign actors to the legality of the use of force, or by bringing together already existing obligations. It questions to what extent there is a legal void to which the concept would respond. It further discusses dilemmas that the concept may pose in relation to the ad hoc and neutral character of post-conflict reconstruction, including existing rules on responsibility for post-conflict reconstruction.