There is growing concern over permanent blackouts caused by high altitude electromagnetic pulse (HEMP) generated from a high-altitude nuclear explosion (HANE). Despite being a type of nuclear attack, the issues raised by HEMP attacks and specific measures against them have been absent from the discourse on international security policy, and unaddressed in past nuclear disarmament and non-proliferation efforts. With proliferation of nuclear weapons remaining unchecked in today?s security environment, this article argues for the necessity to examine measures against HEMP attacks and against cascading blackout effects. Furthermore, it calls on the international community to reach a shared understanding that the threat of HEMP is a humanitarian issue of nuclear weapons, and to create international norms that prohibit HEMP attacks.