Proliferation is here to stay, and President Obama’s promise of “a world without nukes,” which won him the Nobel Prize in 2009, now seems almost fraudulent. Ironically, international law has managed to outlaw the poisoned arrow and the dumdum bullet, the land mine and the cluster bomb, but nuclear weapons have thus far been too hot for it to handle. It is plain that their use is a breach of the law of war: their ionizing radiation cannot distinguish between soldier and civilian, military target and hospital or school. They cause unnecessary and disproportionate suffering, and they pose an existential threat to the environment. Even a limited war—for example, between India (which has 100 nukes) and Pakistan over Kashmir, or between North Korea and the U.S.—would probably change the climate before climate change changes it.

But how is the problem of proliferation to be addressed, short of opportunistic use of force by America and its allies on countries like Iran? Many states (the movement is led by Mexico) plan to make the acquisition of nuclear weapons a crime against humanity by amending the treaty of the International Criminal Court at its review conference in 2016. That would entitle the Security Council to authorize an attack on Iran or any other country outside the nine that already possess nuclear weapons to stop it from assembling a bomb. But this will have to be accompanied by a binding agreement between the nuclear-armed states gradually to reduce the number of nukes in their arsenals to zero and by the establishment of a powerful U.N. inspection agency to replace the toothless IAEA, which cannot inspect suspicious facilities, in Iran or elsewhere, without permission of the suspect state.

Whether our children will live in a world without nukes depends on whether the international community can be made sufficiently fearful of a nuclear war to reach an agreement on gradual but complete disarmament.