This article considers the international legal obligations relevant to States when withdrawing from situations of armed conflict. While a growing literature has focused on precisely when armed conflicts come to a legal end, as well as obligations triggered by the cessation of active hostilities, comparatively little attention has been paid to the legal implications of withdrawals from armed conflict and the contours of the obligations relevant to States in doing so. Following in the wake of just war scholarship endeavouring to distil jus ex bello principles, this article examines States’ obligations when ending their participation in armed conflicts from the perspective of international humanitarian law (IHL). It shows that while it is generally understood that IHL ceases to apply at the end of armed conflict, this is in reality a significant simplification; a number of obligations actually endure. Such rules act as exceptions to the general temporal scope of IHL and continue to govern withdrawing States, in effect straddling the in bello and post bellum phases of armed conflict. The article then develops three key end-of-participation obligations: obligations governing detention and transfer of persons, obligations imposed by Article 1 common to the four Geneva Conventions, and obligations relating to accountability and the consequences of conflict.

This article discusses some of the challenges related to the beginning of application of international humanitarian law (IHL). It concludes that IHL pertaining to international armed conflicts begins to apply as soon as one State employs force in the territory of another State without the latter's consent, provided that the violence is of a collective nature. In the case of non-international armed conflicts, this article acknowledges that it is now well settled that the two key criteria are the organization of the parties to the conflict and the level of intensity of the violence. This article shows however that some of the challenges inherent to the beginning of application of IHL make it almost impossible to identify a very single point in time at which it begins to become applicable, be it for international armed conflicts, including occupation, or non-international armed conflicts.

This article provides an overview of the rules governing the end of application of international humanitarian law (IHL), or the law of armed conflict. It articulates the general principle that, unless there is a good reason of text, principle or policy that warrants an exception, the application of IHL will cease once the conditions that triggered its application in the first place are no longer met. For IHL to apply, its distinct thresholds of application – international armed conflict, belligerent occupation and non-international armed conflict – must continue to be satisfied at any given point in time. The article also examines situations in which a departure from the general rule is warranted, as well as the factors that need to be taken into account in determining the end of each type of armed conflict. In doing so, the article analyzes terminating processes and events, which generally end the application of IHL (but not necessarily all of it), and transformative processes and events, which end the application of one IHL sub-regime but immediately engage another. Finally, the article briefly looks at the (putative) armed conflict between the United States and Al Qaeda and its seemingly imminent end.