At 8.30am on September 20th, 2017, President Michel Temer of Brazil sat down at a ceremonial table inside United Nations headquarters in New York and signed the Treaty on the Prohibition of Nuclear Weapons.

Brazil thereby became the first country to legally commit itself to the total renunciation of nuclear weapons. This means not only renouncing any research, development, manufacture, or deployment of nuclear weapons, but also refusing to assist any other party engaging in those activities.

Whatever your view of the current Brazilian government, this commitment is significant. Brazil is one of the 13 countries of the world which, at one time or another, started developing their own nuclear weapons and then abandoned them.

Brazil is also one of the 37 countries of the world able to develop nuclear weapons within a matter of months if they chose to. Of those, Brazil was considered – until September 20th of this year – one of a small handful of countries most likely to develop nuclear weapons in the next 10 years.

By signing this new Treaty, Brazil has made a legally binding commitment not to do so. As of September 28th, another 52 UN member states had also made that commitment, including South Africa – the only country to have built and tested nuclear weapons and then abandoned them.

Who supports the treaty?

There are 195 member states in the United Nations.  Of these, 137 were present at the treaty negotiations in spring and summer 2017.  On July 7th, 122 of them voted in favor of the final text of the treaty, one abstained (Singapore), one voted against it (Netherlands). Thirteen countries were not present for the final vote and eleven countries voted in favor of the negotiations but then did not take part in them.  That makes a total of 146 potential signatories at the present time.

Of the nine nuclear weapon states, North Korea actually voted in favor of negotiations. China, India and Pakistan abstained. The US, UK, France, Russia and Israel boycotted the negotiations along with a number of their closest allies.

Some of the countries most vehemently opposed to the treaty at the moment are quite likely to sign on to it if and when they have a change of government. Norway, for instance, a NATO member and key ally of the United States, was nonetheless the key instigator of the entire process leading up to this treaty back in 2013.

In the medium to long term, the big question is whether public pressure from below can outweigh the US pressure from above in countries like Norway and the Netherlands. Canada, Australia, Germany and Japan also have strong popular movements against nuclear weapons.

Even the UK, the US’s closest nuclear ally, is likely to sign this treaty sooner or later. Jeremy Corbyn, leader of the main opposition party in the UK and on course to become the next Prime Minister, is a lifelong campaigner for nuclear disarmament.

What is new about this treaty?

The significance of the nuclear ban treaty does not simply lie in the fact that so many countries outside of the United States have indicated their support for the total abolition of nuclear weapons. There is nothing new about that.

In fact, there are resolutions in the UN General Assembly every single year calling on all states to renounce and eliminate their nuclear weapons. These are passed by huge majorities. Sometimes (when the language is vague enough to suit them) even the nuclear weapon states vote in favor of these resolutions and they get passed unanimously.

Ever since the Non-Proliferation Treaty (NPT) was signed in 1968, the US and other nuclear-armed nations have formally and legally committed themselves to the (eventual) elimination of all their nuclear weapons. Meanwhile, the rest of the world has grown impatient waiting for this to happen – hence the impetus for this new treaty.

What is new today is that, for the first time, these fine words and UN resolutions are being set in stone with a legally-binding treaty that requires all states who sign the treaty to have nothing whatsoever to do with nuclear weapons.

This means prohibiting planes with nuclear weapons in their airspace, prohibiting ships with nuclear weapons from entering their territorial waters, and denying access to these countries for military exercises involving nuclear weapons.

Most importantly, it means rejecting the whole theory of nuclear deterrence, because the threat to use nuclear weapons is specifically prohibited by the treaty.

Any nuclear-armed country wanting to sign the treaty must convince the rest of the world that they have irreversibly eliminated their nuclear weapons – or have a legally-binding, time-bound plan to do so.

Verifying whether a country has given up its nuclear weapons or is secretly developing them is a much simpler task than most people think. Mechanisms for doing this are already in place through the International Atomic Energy Agency. And as we know from recent experience in North Korea, no country can test a nuclear weapon – or even a missile capable of carrying a nuclear weapon – without the rest of the world knowing about it.

What about the US?

Clearly, the current US administration has no interest in signing this treaty. Instead, they are actively pursuing a $1.2 trillion dollar revamping of the entire US nuclear arsenal and could even be about to actually use nuclear weapons – for the first time since 1945 – in a war against North Korea.

Nevertheless the US, like every other country in the world, should sign this treaty.

When President Trump declared he was pulling the US out of the Paris Climate Accord, states and cities across the US decided they would commit to fulfilling the Paris commitments themselves, bypassing the federal level altogether. The same approach could be applied to the nuclear ban treaty.

There is no reason why cities, states, businesses, universities and other institutions across the United States should not commit themselves to complying, to the extent possible, with the Treaty on the Prohibition of Nuclear Weapons.

This would not be about issuing eloquent statements in support of nuclear disarmament and the eventual goal of a nuclear weapon-free world. This would be about undertaking a verifiable and irreversible elimination of anything to do with nuclear weapons within the jurisdiction or purview of the authority concerned.

It would mean looking very seriously at where nuclear weapons are stored, deployed or transported around the country and insisting that these are removed.

It would mean looking at investment portfolios, at companies that may contribute parts for nuclear weapons or their delivery systems, at university research programs that are advancing the development or further refinement of nuclear weapons technology.

This may sound like a step too far for some – or too unrealistic for others. But these are weapons of mass destruction. They threaten the very survival of humanity on this planet.

It is already illegal under existing international law to use these weapons and by signing this new treaty it becomes illegal even to possess them. We can and must take all necessary steps to move towards their total elimination.