The outlook for nuclear arms control is desolate in all three of its dimensions – risk reduction, non-proliferation and outright elimination. The important agreements of the past are dead or on life support. And the recent behaviour of the actors that matter most – the United States, Russia and China – has fed concerns things can only get worse.The nine nuclear-armed states possess between them more than 12,200 nuclear warheads, with a combined destructive capacity of more than 145,000 Hiroshima bombs. Some 9,000 of these are militarily active or deployed. Alarmingly, some 2,000 US and Russian weapons remain on dangerously high alert, ready to be launched within a decision window for each president, if their country is perceived – rightly or wrongly – to be under nuclear attack, of just four to eight minutes. The US and Russia, holding between them 90% of the global stockpile, dramatically downsized their inventories after the end of the Cold War. But that momentum has completely stalled. Every nuclear-armed state is now modernising or increasing its arsenal. This is especially true of China, whose inventory has doubled in a few short years to nearly 600 weapons, with new land- and seaborne delivery systems.More troubling still, the longstanding taboo against the use of nuclear weapons may be weakening, with Russia’s President Vladimir Putin in particular talking up this prospect in the Ukraine war in language not heard since the height of the Cold War. A number of states are considering using nuclear weapons – especially so-called “tactical” weapons – not just for deterrence but for warfighting. Read more: Russia’s nuclear strategy in Ukraine isn’t deterrence – it’s terror As agreements die, the threat risesThe big arms-control agreements of the past, which – at least between the US and Russia – banned certain systems outright, set constraints on deployments and built confidence through transparency, are now dead. These include the Anti-Ballistic Missile and Intermediate-range Nuclear Forces treaties. With the expiry in February 2026 of New START, the 2010 Strategic Arms Reduction Treaty, Russia and the US are without any limit on their nuclear forces for the first time in more than 50 years. Moreover, crucial multilateral treaties are only barely alive. Both the US and Russia have withdrawn from the Open Skies Treaty. The Comprehensive Nuclear Test Ban Treaty, though operating in practice, has still not been finally ratified. Alarmingly, US President Donald Trump has floated the prospect of the US ignoring its prohibitions. And the Treaty on the Non-Proliferation of Nuclear Weapons is in as fragile a condition as it has ever been. The loss of confidence in Washington’s willingness to deliver on its extended nuclear – or even conventional – deterrence commitment to close allies has led to serious discussion in South Korea, and even in some quarters in Japan, about the need to acquire their own nuclear weapons. Such conversations are also now beginning in Europe.The safeguards system of the International Atomic Energy Agency is still reasonably functional, as are less formal restraint mechanisms such as the Nuclear Suppliers Group and Missile Technology Control Regime. But about the only other good news on the non-proliferation agreement front is that regional nuclear weapon free zone treaties are continuing to hold their own in Southeast Asia (with China at long last agreeing to join), the South Pacific, Latin America, Africa and the Antarctic.When it comes to nuclear disarmament, new heart has been given to campaigners by the Treaty on the Prohibition of Nuclear Weapons. This treaty, agreed by 122 UN member states in 2017 and in force since 2021, bans nuclear weapons outright. But there is less to it than meets the eye. There is still no prospect of it being signed or ratified by the states that matter: the nuclear-armed states, or the “umbrella” states (such as Australia) that believe themselves to be sheltering under their protection. Moreover, nuclear disarmament discussion has become more complicated in recent years. This is due to the increase in dual-use systems, especially ballistic or cruise missiles that could carry either nuclear or conventional weapons, and the emergence of real concerns about the development of weapons in space, hypersonic weapons, lethal autonomous weapons, cyberwarfare and the impact of artificial intelligence generally. Multilateral agreements for most of these new areas have not been even conceptualised, let alone negotiated.Why international law matters more than everThere is much more international law applicable to the threat or use of nuclear weapons than just the various nuclear-specific treaties that are for the most part now dead or on life support. There is the large body of law, starting with the UN Charter, relating to the threat or use of force, prohibiting any cross-border aggression except in legitimate self-defence or with Security Council approval. There is the 1996 Advisory Opinion of the International Court of Justice that decided (albeit by the narrowest of majorities) “the threat or use of nuclear weapons would generally be contrary to the rules of international law applicable in armed conflict, and in particular the principles and rules of humanitarian law”.There is the mass of international humanitarian law, or law of armed conflict, which – particularly in its emphasis on necessity and proportionality – has huge implications for the conduct of nuclear operations. This includes targeting policy, and other dimensions of NC3 (nuclear command, control and communications) generally. International human rights law, especially as embodied in the International Covenant on Civil and Political Rights, has some potential application, as does international law relating to wanton destruction of the natural environment.And there is the large body now of international criminal law, relating to genocide and other crimes against humanity, and war crimes, which sets important new constraints on the freedom of action of individual nuclear decision-makers subject to it. However, when it comes to the application of all this additional constraining international law – critically important as it is protecting the world from the insanity of nuclear conflict breaking out, or doing at least something to mitigate its horror if it does – the unhappy reality is that the whole concept of international law is under greater stress than it has been within any of our living memories. Of all the outrageous assaults on decency perpetrated by Trump, the nadir was possibly his New York Times interview in January 2026, when he said that “I don’t need international law” and that the only constraint on his power as president of the US was “my own morality, my own mind”.Depressing as all this may be, the last thing the world can afford to do – and that anyone with half an instinct for sanity and decency should want to do – is give up on international law. There is no more important time than now than to reinforce the perception that there is huge ongoing utility in understanding the critical role international law has played in the past, and can and should play in the future, in constraining the use of these weapons. They are the most indiscriminately inhumane ever invented and the only ones currently posing an existential risk to life on this planet.In this context, the good news is there is an online course on Nuclear Weapons Law now on offer at the University of Sydney. It is open to all comers worldwide, and aimed at educating on all the ways in which existing international law constrains both the use and threat of use of nuclear weapons, and the critical importance of restoring its salience. It is a long-overdue enterprise, one from which I am now acutely aware that I and my own generation of policymakers and practitioners would unquestionably have benefited.Gareth Evans was Australian Foreign Minister 1988-96, President of the International Crisis Group 2000-09, and Chancellor of the Australian National University 2010-19. He initiated the Canberra Commission on the Elimination of Nuclear Weapons, co-chaired the Australia-Japan International Commission on Nuclear Non-Proliferation and Disarmament, was founding convenor of the Asia Pacific Leadership Network on Nuclear Non-Proliferation and Disarmament (APLN), and co-authored Nuclear Weapons: The State of Play (ANU, 2013 and 2015).