The obligation to ‘respect and to ensure respect’ for the provisions of international humanitarian law is a core legal obligation of every country in the world. The source of this obligation is found both in the Geneva Conventions of August 1949 and their Additional Protocols and in customary international humanitarian law. Although the obligation is well known, its interpretation has been the subject of some debate. Kalshoven (1999, p. 3) described this obligation as a ‘ripening fruit’ that had emerged from a ‘tiny seed’. This chapter explores the continual ‘ripening’ of this ‘fruit’ with a view to further elucidating the meaning and scope of the obligation. It proposes that this obligation be viewed as relevant to notions of global order and disorder because it requires States to consider the cross-border impacts of the actions of other States. The faithful application of this obligation by States can reduce the occurrence of cross-border humanitarian issues created by armed conflict.