Two-thirds of the global child population lives in countries affected by violent and high-intensity conflict. International humanitarian law provides broad protection for children in the event of armed conflict. However, as the 2017 report of the un Secretary-General on children and armed conflict stresses, the scale and severity of grave violations has increased. This paper addresses the central puzzle of why the existing legal and normative frameworks of child protection have achieved so little, in addressing the marginalisation and disempowerment of children in armed conflict. We argue that the contemporary application of r2p in protecting children will be limited unless at least two fundamental challenges are met: (a) taming power politics; and (b) squaring inherent contradictions between the global r2p norm and national and regional normative frameworks of child protection. We highlight the case of Japan to illustrate the limits of the contemporary application of r2p in protecting children.