Dr Andrew G Jones, Lecturer in law, Coventry University

When Honduras ratified the Treaty on the Prohibition of Nuclear Weapons on 24 October 2020, the nation became the 50th country to do so. This activated the Treaty’s entry into force provision, meaning that it would become active 90 days later, on 22 January 2021, less than 4 years after its adoption in June 2017.

This has been hailed as a big step in the fight against the threat of devastation that comes with nuclear arms. As the UN Secretary General, António Guterres, said in a statement, the entry into force of the treaty “is the culmination of a worldwide movement to draw attention to the catastrophic humanitarian consequences of any use of nuclear weapons. It represents a meaningful commitment towards the total elimination of nuclear weapons, which remains the highest disarmament priority of the United Nations.”

The Prohibition Treaty joins the already active Non-Proliferation of Nuclear Weapons Treaty, the world’s most widely ratified arms limitation and disarmament treaty, with 191 States Parties. This latter document has been in force since 1970, and works to prevent the spread of nuclear weapons, whilst also encouraging disarmament and calling for a treaty on general and complete disarmament; a treaty that is now a reality.

Impact of the Treaty

The fanfare that has accompanied the 50th ratification is understandable. The Prohibition Treaty is certainly a step in the right direction in terms of nuclear arms. Its extensive first Article prohibits the development, testing, production and transfer of nuclear weapons, requires States not to stockpile nuclear weapons and, perhaps most crucially, part (d) prohibits the use or threat to use nuclear weapons or other nuclear explosive devices.

Article 2 obligates States to report on whether they possess or have possessed nuclear weapons, whether they are present on their territory and whether they have eliminated any nuclear-weapons programmes or facilities. There is also a requirement to cooperate with procedures to verify the elimination of all such programmes in Article 2.

These elements are of vital importance to global efforts to steer away from the threat of nuclear war which has plagued humanity since the end of the Second World War. It is fitting, therefore, that the series of ratifications that have brought it to this point come as the world commemorates the 75th anniversary of the end of the Japanese campaign in 1945. The only time in history which saw the deployment of nuclear weapons outside of testing, resulting in the deaths of more than 200,000 people in just two attacks.

In addition, there is an undertaking within Article 6 of the treaty for States to provide assistance to the victims of the use of testing of nuclear weapons, including medical care, rehabilitation, psychological support and social and economic inclusion. This same Article also calls on States to  ’take necessary and appropriate measures towards the environmental remediation’ of areas under their control that have been contaminated the use of nuclear weapons.

An End to Nuclear Arms?

The Treaty’s provisions build upon the foundation of existing principles of international law that apply to nuclear weapons. The Non-Proliferation Treaty already prohibits the transfer of nuclear weapons, as well as their development. However, this only applies to those States that do not already have such weapons at the time they become subject to the limitations. For nuclear armed States, the obligation is merely to refrain from supplying other nations with arms, and to not encourage or facilitate development.

The more absolute terms of the Prohibition Treaty do not allow for such an exemption, applying to all States equally. However, there is a rather obvious flaw with this; with such a clear prohibition, it is hardly surprising to see that the nuclear armed nations have opted not to make themselves subject to the treaty.

Since international law works on the basis of State consent, and since the 8 world’s nuclear armed states – USA, UK, France, China, Russia, India, Pakistan, North Korea and Israel – have not signed the treaty, it seems that the prohibition will actually have little impact.

Non-nuclear armed States are already prohibited from developing and stockpiling nuclear arms, so a second prohibition merely reaffirms this existing legal regulation, adding strength to the call for disarmament. However, without the agreement of the world’s 8 nuclear armed countries, the prohibition is as much symbolic of the drive to eliminate nuclear weapons as it is an effective legal hurdle at this point.

This is especially true given the well-established pattern of behaviour of nuclear powers when it comes to the development of nuclear weapons. Recent years have demonstrated the lengths to which countries like the USA might be willing to go to prevent other States from attaining nuclear arms.

For now, however, this new element of international law will have little real impact on the legality of nuclear arms for those who already possess them. Nonetheless, it is a much-needed signal of the world’s position, especially with the expiration of the START Treaty, which limits the size of the US and Russian nuclear stockpiles, fast approaching.

Is the Use of Nuclear Arms Legal?

As already mentioned, perhaps one of the most important elements of the treaty’s prohibitions is that States cannot use or threaten to use nuclear weapons. This means that the threat of nuclear war is essentially nullified, as much as anything ever is, by a clear provision of international law.

This again builds upon already existing norms of international law. Enshrined in Article 2(4) of the Charter of the United Nations, the prohibition of the threat or use of unilateral force in general is considered a cornerstone of the international legal system. This element of the law essentially establishes the simple rule that no country can either threaten or use aggressive armed force against another.

The Charter’s prohibition, however, does have an exception. Under Article 51, a State might be permitted to use of force as a necessary and proportional act in self-defence where it has been the victim of an armed attack. In such circumstances, the force used will be considered justified, and therefore not a breach of international law, provided it is limited to the purpose of nullifying the threat which justifies it.

With this being the case, it is perhaps surprising that the use of highly destructive and entirely indiscriminate nuclear weapons has not been conclusively ruled out by international law.

In fact, the potential use of such weapons was directly considered by the International Court of Justice in 1996. In its landmark Advisory Opinion on the Legality of the Threat or Use of Nuclear Weapons, the ICJ considered the various impacts of nuclear weapons, recognising that it would be difficult to reconcile their nature with the limitations provided in both human rights law and the law of armed conflict.

Despite this, the Court’s ultimate opinion on the matter was that in a situation which threatened the survival of a nation as a whole, the right to self-defence potentially included the right to use nuclear weapons. As such, the judges concluded that they ‘[could not] reach a definitive conclusion as to the legality or illegality of the use of nuclear weapons by a State in an extreme circumstance of self-defence, in which its very survival would be at stake.’ This left open the possibility of using nuclear weapons in cases of extreme self-defence.

With the entry into force of the Prohibition Treaty, it seems that the potential to unleash these weapons has now been closed, at least amongst those 50 ratifying States. Unlike the general prohibition of force, the treaty allows no exceptions to its prohibitions. The absolute language of the first article makes it clear that nuclear weapons can never be used ‘under any circumstances.’ This removes even the limited possibility of extreme self-defence where the life of the nation is under threat.ConclusionOverall, the Prohibition is certainly something to be celebrated. Its entry into force demonstrates the continued development and acceptance of the view that nuclear weapons and their use in any circumstance is not acceptable. Many of the core provisions build upon existing international norms, carrying the international legal regime in this area forward, and strengthening the protections already in place.

However, while celebration is certainly warranted, real change of the situation with regard to nuclear weapons will only occur with the compliance of the already nuclear armed nations; currently a somewhat unlikely eventuality. For now, the treaty signals the declared aspiration of the world to see the elimination of nuclear weapons and nuclear weapons programmes. The treaty calls upon parties to it to encourage its acceptance by all states, with the aim of achieving universal adherence to its provisions. Ultimately, this should surely be an aim that should be supported by the international community as a whole. Where such wide acceptance can be achieved, the Treaty has the potential to make a significant contribution to the development of a customary norm prohibiting the threat or use of nuclear arms in all circumstances. Today, this remains aspirational, yet this step forward at least demonstrates that progress is being made in this direction.