This article provides a critical examination of the debate over the relationship between international humanitarian law and international human rights law. On the question surrounding the very fact of co-application, it appears that the dominant view supports the co-applicability of the two legal regimes. Opinion is however far from settled on the scope of application of international human rights law, especially insofar as it relates to the issue of extra-territorial applicability. The approach taken in the event of co-applying the two frameworks to specific circumstances, and whether and how one is to use the doctrine of lex specialis, reveals further questions in need of coherent answers. Finally, there remain particular areas in which the co-application faces challenges that must be surmounted, if it is to prove a useful approach. These include the issues of the so-called “war on terror,” the distinction between the jus ad bellum and the jus in bello, non-international armed conflicts, and more. Whilst the co-application of the two regimes is now almost undisputed, it appears therefore that obstacles remain that must be dealt with in order for the relationship of the regimes to be of a fully harmonious nature.