Trump’s administration has been marked by systematic attacks on international treaties and institutions. This pattern is so extensive that it is commonplace to suggest that the international rules-based system is breaking down.

This deterioration can be seen from the Paris Climate Agreement to the World Health Organisation, big hitters almost universally recognised as essential; but also in UNESCO, UNHRC and UNRWA – to many of us just acronyms, but actually vital international institutions, defending cultural heritage, protecting human rights and aiding refugees. The agreements which underpin these institutions, as well as many others, have fallen foul of Trump’s international policies.

But Trump’s withdrawal syndrome has also extended to arms control agreements. In 2018 he pulled the US out of the Iran nuclear deal, in 2019 it exited from the Intermediate Range Nuclear Forces (INF) Treaty, and this year this was followed by the Open Skies Treaty. His actions have opened the door to nuclear proliferation and to a new nuclear arms race.

This cavalier approach to global security has little popularity. Even the UK – usually the US’s closest ally on nuclear matters – has stuck with the Iran nuclear deal and urged retention of the INF Treaty. For the global majority of states that back nuclear disarmament – around half the globe is already self-organised in nuclear weapons-free zones – Trump’s actions are increased evidence of the need for a new global framework of disarmament.

For some years a process has been underway in the United Nations, largely brought into being by states from the Global South, to make nuclear weapons illegal under international law. The proposal is to ban them in the same way that chemical and biological weapons are outlawed – and, finally, the work done to this end has reached some fruition.

Yesterday, Honduras became the 50th state to ratify or accede to the UN’s Treaty on the Prohibition of Nuclear Weapons (TPNW). It will enter into international law in 90 days. The treaty constitutes a comprehensive ban on nuclear weapons and other related activity, and its list of prohibitions includes the use, stockpiling, testing, production, manufacture, stationing and installation of nuclear weapons.

This is a significant development – for the first time, legislation exists which rules nuclear weapons to be illegal. Previous international legal opinion which came from the World Court in 1996 indicated that under virtually all circumstances it would be illegal to use them – but not to possess them.

Of course, there are limits and obstacles to overcome before the treaty fulfils its transformative capacity. Only those states that have ratified the treaty are bound by it – although there are likely to be wider restraints as a result – and the nuclear weapons states have largely boycotted its negotiating process.

The US and UK ambassadors have gone so far as to stand outside the UN negotiating room denouncing the talks and there is clear evidence that the US and UK have pressurised other states, notably including potentially sympathetic NATO members, not to engage with the TPNW.

Most interestingly, last week it was widely reported that the US has been urging ratifying states to withdraw their support, to prevent the treaty coming into force. A letter to signatories obtained by The Associated Press makes clear the opposition of the five original nuclear powers: the US, Russia, China, Britain and France, as well as America’s NATO allies.

The letter says that these countries ‘stand unified in our opposition to the potential repercussions’ of the treaty. It also repeats the mantra that has been issued from hostile governments over the past few years – that the TPNW is a danger to the nuclear Non-Proliferation Treaty (NPT), the supposed cornerstone of global non-proliferation efforts.

This, of course, is nonsense. The NPT calls for the complete disarmament of nuclear weapons but includes no practical plan to make that happen. In the 50 years of its existence, any initiatives towards disarmament have hit the brick wall of nuclear state opposition.

It is precisely because of the failure of the NPT that much of the global community has brought forward the TPNW as a nuclear ban treaty. It’s a bit rich of the nuclear weapons states to claim to defend the NPT when they have effectively sabotaged it. Although they have been dismissive of the TPNW, it’s clear they are now rattled by it.

So the TPNW and its imminent entry into force is very good news – for the collective determination of the global majority of peoples and states, and as a step towards dealing with the very real threat of nuclear annihilation that hangs over all our heads.

It’s a welcome antidote to Trump’s trashing of treaties. Now the real work commences to make it impact on the nuclear weapons states – including our own in the UK.