Nuclear Weapons, Uncertainty And The Law World Court Project UK

The Public Conscience in Action

Secretary: George Farebrother, 67, Summerheath Rd, Hailsham, Sussex, UK BN27 3DR

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The World Court Project is an international citizens’ network which is working to publicise and have implemented the July 8 1996 Advisory Opinion of the International Court of Justice

There is good reason to believe that any threat or use of a 100 kiloton UK Trident warhead would be open to serious legal doubts. The Government responds by stating that “the United Kingdom’s minimum nuclear deterrent is entirely consistent with international law”. However, we need more information before we can assess the validity of this claim. Answers to several questions are required..

The Government Case

If challenged about the legality of Trident, the Government uses the following arguments:

-  the 1996 Advisory Opinion of the International Court of Justice (ICJ) did not rule that the threat or use of nuclear weapons would be illegal.
-  the legality of the potential use of nuclear weapons is to be determined by the criteria which apply to any form of weapon.
-  the determining factor is the specific circumstances in which they are to be used.
-  hypothetical speculation about such circumstances serves no useful benefit.

These arguments were developed in the written and oral submissions made by the UK and US to the ICJ in 1994 and 1995 when it was considering requests by the World Health Organisation (WHO) and the UN General Assembly (UNGA) for Advisory Opinions on the legal status of the threat or use of nuclear weapons.

Nuclear Weapons In General?

The arguments in the submissions all refer to nuclear weapons generally, and never to specific types. This is not surprising as the requests for Advisory Opinions were couched in general terms. Letters to the Government about Trident are therefore usually met with replies about nuclear weapons in general. However, if, as is generally accepted, nuclear weapons are subject to the same legal restraints as any form of weapon, then discussion in the UK must revolve around Trident, the only nuclear weapon system it deploys.

Hypothetical Situations

In spite of the Government’s reluctance to entertain hypotheses, the ICJ submissions contain references to possible legal use. Speaking for the UK in November 1995, Attorney General Sir Nicholas Lyell said, “Let me take an example. A State or group of States is faced with invasion by overwhelming enemy forces. That State or that group of States is certainly entitled to defend itself. If all the other means at their disposal are insufficient, then how can it be said that the use of a nuclear weapon must be disproportionate?” The US oral statement referred to situations “such as a small number of accurate attacks by low-yield weapons against an equally small number of military targets in non-urban areas”. The UK written statement on the WHO request claimed that “modern nuclear weapons are capable of precise targeting and many are designed for use against military objectives of quite small size”. The emphasis is on limited use of low-yield weapons.

On 15 November 2000, during the Lord Advocate’s Reference proceedings arising out of the Greenock case, Duncan Menzies QC, Advocate Depute for the Crown, provided an interesting example of the possible legal use of UK Trident: ” … if the nuclear power aggressor was threatening the territorial integrity of a non-nuclear victim state, let’s take it, the example of China being a nuclear power threatening New Zealand, a non-nuclear power, with a battle fleet armed with nuclear missiles which it was stating it was about to fire at New Zealand and which battle fleet was in the Pacific, approaching the point at which the state of New Zealand was in range of its nuclear missiles, in such a situation I submit that it would be consistent with international law, including humanitarian laws applicable to armed conflict, for another nuclear power to use nuclear force against that battle fleet…” Already, questions arise:

1. Why was the UK Trident system, with its 100 kiloton warheads, not referred to in the UK submissions to the ICJ?

2. Would the Ministry of Defence endorse the example provided by Duncan Menzies QC of how Trident might be used lawfully?

Doubts about Certainty

The US and UK submissions consistently presuppose that those arguing for illegality claim that all nuclear weapons have certain “inherent” characteristics which inevitably make their threat or use incompatible with international humanitarian law. Thus the UK written statement on the WHO request refers to “those who maintain that any resort to nuclear weapons by a state which is attacked will inevitably lead to an escalation in the conflict …”, and “It has sometimes been argued that the use of nuclear weapons would inevitably violate this principle” [Unnecessary Suffering]. In referring to the principle that civilian populations must not be made the object of attack, the UK claims that “the essence of this argument is that nuclear weapons cannot be used in a way which enables a distinction to be drawn between combatants on the one hand and civilians and civilian objects on the other. They are thus said to be inherently indiscriminate weapons”. [emphases added]

These are not isolated examples: the submissions are full of such language.

We can accept that nothing can be predicted with certainty. However, a successful challenge to the UK Government’s position would not have to show that any threat or use would be inherently illegal under any circumstances. It would only need to show the improbability of lawful threat or use in any plausible scenario. Although nuclear weapons are subject only to the same legal restraints as any other weapon, the ICJ stated that because of the “unique characteristics of nuclear weapons … the use of such weapons in fact seems scarcely reconcilable with respect for [the principles and rules of law applicable in armed conflict].”

If this is true of nuclear weapons in general, it must apply all the more forcefully to a 100 kiloton Trident warhead.

Risk Assessment

From publicly available documents and correspondence with the Government, we still have little idea of how it estimates risk. Risk assessment means estimating the probability of a decision having an unintended but pernicious outcome, and multiplying it by the seriousness of that outcome. A small risk of a disaster would weigh more heavily than a moderate risk of a minor problem. With just one 100 kiloton Trident warhead, let alone the current load of three in each UK missile, the outcome could be catastrophic.

The ICJ recognised that “The destructive power of nuclear weapons cannot be contained in either space or time. They have the potential to destroy all civilization and the entire ecosystem of the planet”. However small the probability of such an outcome on a particular occasion, the enormity of a potential catastrophe produces a result beyond the limits of human calculation.

What is at issue here is the risk of contravening international humanitarian law. In her Dissenting Opinion, Judge Higgins pointed out: “There has been considerable debate, as yet unresolved, as to whether this principle [that civilians may not be the target of attack] refers to weapons which, because of the way they are commonly used, strike civilians and combatants indiscriminately or whether it refers to whether a weapon, ’having regard to (its) effects in time and space’ can ’be employed with sufficient or with predictable accuracy against the chosen target’ “. Her first alternative would tend to outlaw nuclear weapons in general. Her second one requires examination of particular nuclear weapon systems.

To be convincing, the Government must therefore argue that the risk of law-breaking arising from the threat or use of Trident is almost zero. It must be shown that any use of Trident would carry virtually no risk of nuclear escalation, serious damage to neutral states, or disproportionate civilian casualties. There must be practically no question of missing the target due to variations in the weather, microscopic blemishes on the delivery vehicle or minor faults in the guidance system.

We must also bear in mind that our experience of nuclear detonations on civilian populations is limited. There have only been two (Hiroshima and Nagasaki), in both of which the destructive power was less than a fifth of a Trident warhead.

The same approach applies to any possibility that a Trident missile might be launched by accident or miscalculation. It is not sufficient to claim that such a possibility is very remote. It must be shown to be effectively excluded over the whole lifetime of the system. We must be convinced that there is no room for human error. Unless this is true, the deployment of Trident amounts to recklessness.

The next questions are therefore: 3. Without a serious and publicly available probability analysis of the potential results of a Trident strike, how can the Government assure us that no threat or use of Trident could risk violating the law?

4. Is the Government confident that Trident could be used with sufficient or predictable accuracy against the chosen target?

Balancing the Consequences

Sir Nicholas Lyell told the ICJ that ” … even a military target must not be attacked if to do so would cause collateral civilian casualties or damage to civilian property which is excessive in relation to the concrete and direct military advantage anticipated from the attack – an aspect of the wider principle of proportionality to which I have already referred”, but that “this rule requires a balance to be struck between the concrete and direct military advantage anticipated and the level of collateral civilian casualties and damage foreseen” and “the greater the military advantage which can reasonably be expected to result from the use of a weapon in a particular case, the greater the risk of collateral civilian casualties which may have to be regarded as within the law”. Clearly a balance between military advantage and collateral damage is envisaged. This is the crux. We accept that, in the nature of things, no future scenario can be foreseen precisely. However, we have been assured that “…legal advice would also be available to Ministers if circumstances were extreme enough for us ever to have to consider the use of nuclear weapons to defend ourselves from attack. We are satisfied that our arrangements to ensure informed legal advice in such circumstances are fully adequate. …” and “legal advice from the Government’s legal advisers was available to Ministers and senior officers and officials in considering the Strategic Defence Review ” [Douglas Henderson, Minister of State for the Armed Forces, letter to Nigel Waterson MP, in response to a letter from Leslie Dalton, 1 June 1999].

Legal advice in a nuclear emergency would not spring from a vacuum. We can assume that criteria (as opposed to “hypothetical speculation”) do exist for balancing military advantage with collateral civilian casualties in the event of a nuclear strike.

We need to know more about these criteria. Simply to say that legality depends on the balance between military advantage and civilian suffering is not enough. There is the problem of comparing different orders of criteria. The military advantage of destroying a particular target can, in principle, be assessed. In a utilitarian world we can, with great difficulty, imagine how values could be attached to the lives and wellbeing of a specified number of civilians. What seems incomprehensible is how anyone could make the comparison between the value of a very large number of lives and a specific military advantage. We therefore need to understand the government’s procedures and principles for making these assessments. These basic criteria can hardly qualify as state secrets.

We therefore need to know: 5. What are the general criteria for determining the balance between military necessity and suffering to civilians arising from the use of Trident?

6. What are the general theoretical sources of these criteria?

7. Is the Government confident that, even if these criteria were well understood by lawyers and decision makers well beforehand, they could be relied on to provide secure practical, moral and legal guidance during a nuclear emergency?

Effects on People

These criteria must surely include the effect of a 100 kiloton Trident warhead on any civilian population living at or near likely military targets. On 10 January 2000, Jeremy Corbyn MP raised this issue in a question to the Secretary of State for Defence. The answer yielded the information that computer modelling had taken place “which enables us to assess the effects of nuclear detonations”. The factors taken into account included “the yield and design of the weapon used; the accuracy of the delivery system employed; the nature and construction of the target; the characteristics of the surrounding terrain; the height of the detonation; and geological and weather conditions”. The factors listed do not include the crucial one – the likely effects on the civilian population. Without this, neither the public at large nor the lawyers advising the government can make an informed legal assessment. So we have another question: 8. Has any assessment been carried out by the Government of the effects of a 100 kiloton Trident warhead detonation on a civilian population living near a military target? If so, is there any good reason why the results should not be made public?

Nuclear Secrecy

A Ministry of Defence letter has stated:

“nor does the Government believe that any conceptual planning on potential use of nuclear weapons carried out by the Ministry of Defence can reasonably be made open to public scrutiny. Secrecy in this area plays an important part in enabling the United Kingdom to maintain a credible minimum deterrent capability at the lowest possible level.” [Stephen Willmer to Angie Zelter, 2 March 2000].


It is one thing to invoke the need for secrecy in matters of military capabilities and planning. It is quite another to claim it for the legal thinking governing these vital issues. This should be open to democratic accountability. So we need to know: 9. Why does the Government decline to disclose the legal criteria governing the possible use of Trident?

10. If these criteria are treated as secret, how can the courts operate effectively in cases involving citizen disarmament of Trident?

11. How can ordinary citizens, who honestly doubt the legality of the threat or use of Trident, hope to act with probity without access to the Government’s legal criteria?


One aspect of the legal criteria for the threat or use of Trident gives rise to special cause for concern. The US stated orally to the ICJ that “…the customary law of reprisal permits a belligerent to respond to another party’s violation of the law of armed conflict by itself resorting to what otherwise would be unlawful conduct”. The US written statement referred to Additional Protocol 1 to the 1949 Geneva Conventions which contains prohibitions on reprisals against civilian populations. “These are among the new rules established by the Protocol that … do not apply to nuclear weapons”. This view was echoed in the UK oral statement. It is to be hoped that this interpretation does not imply a view that a nuclear reprisal directed towards the civilian population as such could ever be lawful. 12. Can the Government confirm that under no circumstances would Trident ever be even threatened, let alone used, against a civilian population as such?

Legal Scrutiny of Trident Needed

The very least that can be concluded from this assessment is that the legality of Britain’s nuclear policy is open to question. However, on 23 August 1999 George Robertson, then Secretary of State for Defence, wrote to Austin Mitchell MP,

“Thank you for your letter of 22 July 1999 requesting a meeting to discuss the legality of Trident. I am afraid that such a meeting would serve little purpose. We have repeatedly made our position clear. We do not consider the possession or use of nuclear weapons as such to be illegal.” The delegation would have consisted of three MPs and Lord Murray, a former Lord Advocate of Scotland. They had asked for discussion about UK Trident in particular, not nuclear weapons as such. There was a complete refusal to discuss the matter, even with very well-informed and distinguished people, and with no real reason given – merely an unsupported assertion. This is only one of several examples of attempts to raise the issue which have been rejected without proper explanation – which is why we need to ask one more question. 13. Will the Government recognise that the legality of the threat or use of Trident is open to serious doubt and therefore deserves the fullest public scrutiny?