This article addresses the application of international humanitarian law (IHL) and human rights law (IHRL) in peace operations and how this is relevant to the ius post bellum. The author first highlights the challenges in defining the ius post bellum as a legal concept, in particular as regards scope of application, relationship with other areas of international law and content. He advocates a ius post bellum comprising variable rules resulting from the applicability and interaction of other fields of law. The author then analyzes relevant questions of the applicability of IHL and IHRL in peace operations. He submits that each peace operation has a distinct legal framework, which may include IHL and/or IHRL, and that the challenge is forging agreement on which rules apply when and how they interact and should be applied in peace operations. The author concludes that IHL and IHRL are important parts of what one could call a variable ius post bellum.