The achievement of past international treaties prohibiting anti-personnel mines and cluster munitions showed that unpropitious political situations for dealing with the effects of problematic weapons could be transformed into concrete, legally binding actions through humanitarian-inspired initiatives. Although there is now renewed concern about the humanitarian consequences of nuclear weapons, some policy makers dispute the relevance of these past processes. This article examines how and why cluster munitions became widely reframed as unacceptable weapons, and the nature and significance of functional similarities with contemporary efforts of civil society activists to instigate humanitarian reframing of nuclear weapons and promote the logic of a ban treaty in view of its norm-setting value among states. In the case of cluster munitions, the weapon in question was signified as unacceptable in moral and humanitarian law terms because of its pattern of harm to civilians with reference to demonstrable evidence of the consequences of use. Ideational reframing was instigated by civil society actors, and introduced doubts into the minds of some policy-makers about weapons they had previously considered as unproblematic. This is relevant to the current discourse on managing and eliminating nuclear weapons in the Nuclear Non-Proliferation Treaty, in which there is dissonance between the rhetoric of those states claiming to be responsible humanitarian powers and their continued dependence on nuclear weapons despite questions about the utility or acceptability of these arms.