The chapter conceptualises the Responsibility to Prosecute as a norm cluster in itself, encompassing the principles of universal jurisdiction and complementarity, and assesses its bipartite structure. Using this norm cluster framework, it proceeds to investigate how the norm has been contested by Sri Lankan leaders after the country’s 1983–2009 civil war and to show how impunity for war crimes has been made possible in post-conflict context, despite international calls for accountability. It hence explores and illustrates how, through the use of quasi-institutionalised ‘home-grown mechanisms’, the contestation of the international norm of Responsibility to Prosecute occurred by prioritising one founding principle—complementarity—over the other—universal jurisdiction. An implication of this case study is that to fully understand the effectiveness and robustness of an international norm, we should also look into the inherent clustering and linkage dynamics within the norm.