In 1996, the Advisory Opinion of the International Court of Justice concluded, by majority, that the threat to use nuclear weapons, including as affecting civilian populations, was not, as such, illegal under present international law. But it held that nuclear weapons states were obliged, as a matter of urgency, to enter genuine negotiations towards the reduction and destruction of nuclear stockpiles. Such negotiations have not occurred in the 22 years since 1996. On the contrary, in 2018 the two major nuclear powers have committed to increasing and enhancing their nuclear armoury. However, in July 2017, a treaty to ban the use, possession and threat of use of nuclear weapons was introduced into the General Assembly of the United Nations. It is now open for signature and eventual ratification. The civil society organisation that triggered this move, International Campaign to Abolish Nuclear Weapons (I-CAN), was later named laureate of the 2017 Nobel Prize for Peace. Given the ongoing proliferation of nuclear weapons, despite the Non-Proliferation Treaty, the failure of negotiations of the kind required by the International Court of Justice (ICJ) Advisory Opinion and the peril to human survival demonstrated by the Cuban Missile Crisis (1962) and the Soviet (Petrov) Warning Error (1983), should lawyers engage with the urgency of dismantling the huge stockpiles of nuclear weapons? Is it time for this existential challenge to humanity return to the ICJ? Does the law have anything to say about such dangers? In the presence of such catastrophic dangers, need the law fall silent?