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Eighty years ago, the nations of the world came together at the first UN General Assembly meeting, and pledged to eliminate nuclear arsenals. Today, amid renewed geo-political tensions and regional conflicts, the risks of nuclear weapons use are growing. Yet even as some governments plan new investments in nuclear arsenals, a coalition of nations, civil society organisations and international institutions are advancing a different vision, anchored in the Treaty on the Prohibition of Nuclear Weapons (TPNW), which went into effect five years ago.
The TPNW, is the first international agreement to comprehensively outlaw nuclear arms. It has already begun to shift norms, expectations and policies including in countries that have not joined.
Here are five ways the treaty is changing the landscape.
1. Nuclear weapons are now illegal
The TPNW is the first global agreement to fully outlaw nuclear weapons — banning their use, possession, development, testing and the threat to use them. States that join also accept a pathway for the verifiable and irreversible dismantling of nuclear arsenals.
While none of the nuclear-armed states have joined, since its existence more countries have joined the broader nuclear disarmament and non-proliferation regime by negotiating safeguards agreements or joining the Comprehensive Nuclear Test Ban Treaty all of which strengthens the global legal architecture necessary for the total elimination of nuclear weapons. The TPNW reinforces existing non-proliferation agreements and bolsters the international safeguards system overseen by the IAEA. At a time when progress towards disarmament often feels stalled, the treaty provides a clear legal pathway towards a nuclear-weapon-free world.
2. Nuclear justice is now at the centre of global disarmament debates
One of the treaty’s most significant impacts has been its insistence that nuclear policy cannot be separated from the lived experience of those harmed by bombs and tests.
Survivors of Hiroshima and Nagasaki, as well as communities affected by the more than 2,000 nuclear tests, from the Pacific to Central Asia, North Africa to Nevada, now have a say in global forums. Their testimonies have shaped debates not only under the TPNW but also at the UN General Assembly and within the Nuclear Non-Proliferation Treaty process. The treaty has created a dedicated space for affected communities to demand recognition, medical support and environmental remediation.
3. The myth of nuclear deterrence is being called out
For decades, nuclear-armed governments have justified their arsenals by claiming that their threats of massive indiscriminate harm keeps the peace, while also failing to mention countless other contributing factors. Yet, the majority of countries supporting the TPNW argue that this narrative doesn’t stand up to the evidence. Scientific research shows that any use of nuclear weapons (by design, miscalculation or accident) carries extreme risks and causes catastrophic humanitarian consequences.
By grounding the debate in risk assessments rather than military doctrine, the treaty has helped empower states without nuclear weapons to voice their own security concerns. It reframes nuclear policy as a global threat, not a matter reserved for the nine states that hold the bomb.
4. The nuclear weapons debate has become more democratic
The treaty has disrupted long-standing hierarchies in global nuclear politics, where nuclear-armed states and a narrow circle of experts dominated the conversation. Instead, the TPNW has opened the door for all countries, regardless of their size, and paved the way for new voices to emerge by recognising the differentiated impacts of nuclear weapons on indigenous populations, women and children. Treaty meetings have included activists, community leaders and parliamentarians from across the globe. The treaty affirms that because nuclear harm would not stop at any border, everyone has not only a stake but a right to be part of the discussion.
5. Institutional investors managing trillions of dollars are denying the nuclear weapons industry access to their funds
Making a weapon illegal can affect not only its political standing but its financial viability. Since the treaty came into force, hundreds of financial institutions including banks, pension funds and asset managers have pledged to exclude nuclear-weapons producers from their portfolios. Around $4.7 trillion in assets are now off-limits to companies involved in the industry.
Five years after the treaty took effect, nuclear-armed states remain deeply opposed, and continually concerned about the loss of legitimacy around these weapons of mass destruction. But the TPNW has already begun to shift power, reshape the conversation and challenge the presumption that the world must continue to live under the bomb’s shadow.