Legal Opinion

On the Illegality under International Humanitarian Law of Threatened Attacks on Civilian Infrastructure, on the Prohibition of Terrorising a Civilian Population, and on the Potential Criminal Liability of American and British Officials for Assisting Such Conduct

I am aware of Mr Trump’s latest threat to the Iranian Government and people, reported by the BBC at 1:20 pm on Tuesday the 7^th April 2026. This is that “a whole civilisation will die tonight” if Iran fails to comply with American demands. I am as revolted by his threat as any other reasonable man must be. However, rather than denounce him and his associates, I will confine myself to matters within my professional competence. I will consider the legal implications of a threatened American assault on Iranian civilian infrastructure. I will further consider the criminal liability, under international law and domestic British law, of American decision-makers and of any British minister, official, or serviceman who assists in such an assault, including by permitting the use of British bases or facilities.

This Opinion proceeds on the assumption, for the sake of analysis, that American forces, or forces acting within an American command structure, intentionally attack civilian infrastructure in Iran, or undertake acts or threats of violence whose primary purpose is to terrify the civilian population into submission. I do not here consider the wider jus ad bellum question of whether the war itself is lawful. I confine myself to the conduct of hostilities. That is enough. A war may be unlawful in its inception, but still be fought within the laws of war. Conversely, a war alleged to be lawful in inception may be conducted by means that are criminal. It is the second of these questions with which I am concerned.

I. The Relevant Legal Framework

The relevant body of law is that branch of public international law commonly known as international humanitarian law, or the law of armed conflict. If there is an armed conflict between the United States and Iran, the four Geneva Conventions of 1949 apply. So too do the rules of customary international law that bind all states whether or not they have ratified later instruments. The United Kingdom, the United States, and Iran are all parties to the Geneva Conventions.

Additional Protocol I of 1977 is not ratified by the United States. That fact is often mentioned by those who wish to blur the legal position. It does not assist them much. A large number of the Protocol’s central rules, including those concerning distinction, terror, and the protection of civilian objects, are widely accepted as part of customary international law. They therefore bind the United States whether or not Washington is pleased to admit it.

The Rome Statute of the International Criminal Court is also relevant, not because it binds all the actors equally, but because it codifies a large body of conduct already criminal under customary law and because the United Kingdom has incorporated much of it into its domestic law by the International Criminal Court Act 2001. The United States is not a party to the Statute. Iran is not a party. The United Kingdom is. This matters most when one comes to British complicity.

II. The Lawfulness of Targeting Civilian Infrastructure

The cardinal principle of the modern law of war is distinction. Parties to a conflict must distinguish at all times between military objectives and civilian objects. Civilian objects may not lawfully be made the object of attack. The test is not whether an object is useful to a society in wartime. Almost everything is useful. The test is whether it makes an effective contribution to military action and whether its destruction offers a definite military advantage in the circumstances ruling at the time.

That test is narrower than governments at war tend to pretend. It is not enough that an electric grid supplies power to a military headquarters if it also supplies power to a city of hospitals, homes, pumping stations, and sewage works. It is not enough that a bridge may one day be used by military traffic if, at the time of attack, its destruction is chiefly calculated to paralyse civilian movement and deepen social disorder. The law does not permit the reduction of an entire society to darkness and ruin merely because a lawyer in uniform can discover some military relevance at the edge of the picture.

There are, moreover, certain objects whose protection is specially emphasised. The law forbids attacks on objects indispensable to the survival of the civilian population. Food systems, drinking water installations, and related infrastructure are obvious examples. The same reasoning applies, in substance if not always in express wording, to the modern electrical and industrial systems on which large civilian populations depend for life itself. A state that deliberately strikes such targets, not as an incident of a narrowly tailored attack on a military objective but as part of a campaign to force capitulation through misery, is plainly outside the law.

The threatened destruction of power plants and bridges across Iran, if carried into effect as publicly described, would therefore be prima facie unlawful unless each target could be shown, individually and convincingly, to satisfy the strict legal test for military objectives and unless the further requirements of proportionality and precautions in attack were met. A campaign announced in the language of spectacle and punishment would struggle to survive that examination.

III. The Prohibition on Terrorising the Civilian Population

The law goes further. It does not merely protect civilian objects. It forbids acts or threats of violence the primary purpose of which is to spread terror among the civilian population.

That rule deserves emphasis because it is precisely here that the present case becomes especially ugly. There is a difference between a lawful attack on a military objective which frightens civilians as an incidental consequence, and a threat or assault intended chiefly to frighten civilians into demanding surrender from their own government. The first may be a misfortune. The second is criminal.

If a head of state publicly threatens that “a whole civilisation will die tonight,” and if he designates “Power Plant Day” and “Bridge Day” as though announcing some monstrous public festival of destruction, he is not speaking the language of limited military necessity. He is threatening terror. If those threats are then implemented by attacks on infrastructure indispensable to civilian life, the legal character of the operation becomes still clearer. One would be dealing, not with collateral fear arising from legitimate attack, but with violence or threatened violence whose primary purpose is to break civilian morale by terror.

That is forbidden by customary international law. It is forbidden by Additional Protocol I. It has long been treated as forbidden by every serious account of the law of armed conflict. The habit of modern Western governments is to pretend that terror belongs only to insurgents and non-state actors. The law is less sentimental. It recognises that states also terrorise.

IV. War Crimes

Where the above rules are deliberately breached, the conduct amounts to war crimes.

Under Article 8 of the Rome Statute, war crimes in an international armed conflict include intentionally directing attacks against civilians as such and intentionally directing attacks against civilian objects, that is, objects which are not military objectives. These provisions reflect pre-existing customary law and are not mere inventions of the Court. No actual death need occur for the offence to be complete, provided the attack was intentionally directed at protected persons or objects.

If, therefore, power stations, bridges, hospitals, industrial sites, or other infrastructure are deliberately attacked in order to impose suffering on the civilian population or to compel political surrender by fear, the legal description is straightforward. The attack is not rendered lawful because it is announced by a president rather than a militia commander, or because it is dressed in the language of security. One may add that repeated or widespread attacks on civilian infrastructure, especially when they produce uninhabitable conditions, may also raise the question of crimes against humanity if committed as part of a widespread or systematic attack on a civilian population. That takes the matter beyond battlefield illegality into the darker territory of organised state criminality.

V. The Potential Criminal Liability of American Leaders and Servicemen

In principle, those who order, plan, authorise, or execute such attacks may incur individual criminal responsibility.

If an American president publicly threatens unlawful violence and unlawful violence follows, his own words may become evidence of intent. Ministers and senior military commanders may be liable either because they ordered the acts directly or because they knew, or should have known, what was being done and failed to prevent or punish it. This is the settled doctrine of command responsibility. The lower ranks may also be liable if they carry out manifestly unlawful orders. An order to target civilians or civilian infrastructure for the purpose of terror is generally of that character. “I was only obeying orders” is a defence of very limited value in such circumstances.

The practical difficulty is jurisdiction. The International Criminal Court cannot presently exercise automatic jurisdiction over American nationals for acts committed on Iranian territory, because neither the United States nor Iran is a party to the Rome Statute. Iran could, however, accept the Court’s jurisdiction by a declaration under Article 12(3). That would materially alter the position. A United Nations Security Council referral is theoretically possible, but in practice fanciful, because the United States would veto any such attempt.

Outside the ICC, one must look to universal jurisdiction in national courts, ad hoc tribunals, or domestic American law. The first exists in theory and occasionally in statute. The second requires political circumstances that do not presently exist. The third depends on the willingness of the American state to prosecute its own leaders for crimes it presently celebrates. One need not dwell overlong on the prospect.

Thus the legal liability is clear in principle, but the likelihood of enforcement is low. That is not unusual in the history of great powers. Their crimes are not usually hidden. They are merely unpunished.

VI. The Liability of British Ministers, Officials, and Servicemen

The position of British actors is materially different and more dangerous for them.

The United Kingdom is a party to the Rome Statute. It has enacted the International Criminal Court Act 2001. It has domestic jurisdiction over war crimes and related offences in a range of circumstances. It is also bound, as a matter of state responsibility, not to aid or assist another state in the commission of internationally wrongful acts where it knows the circumstances of the wrongdoing.

This means that British ministers or officials who knowingly permit the use of British bases, airspace, facilities, intelligence, logistics, or other support for operations that amount to war crimes may themselves incur liability as aiders or abettors. The same may apply to British military personnel involved in operational support, targeting, coordination, refuelling, or base management, if they know that the assistance they provide is contributing to unlawful attacks.

The law here is not obscure. Aiding and abetting requires assistance rendered with knowledge of the essential circumstances. It does not require that the aider share every motive of the principal offender. If British territory is knowingly placed at the disposal of an unlawful campaign against civilian infrastructure, the comforting formula that Britain is only providing “defensive support” will not save those involved if the underlying operation is plainly criminal.

The point should be put with complete bluntness. If American aircraft or missiles are launched from British bases, or materially supported through British facilities, for the purpose of carrying out attacks that intentionally terrorise the Iranian civilian population or destroy civilian infrastructure outside lawful military necessity, then the British state is not a spectator. It is an accomplice. And those within it who make, authorise, or implement such decisions may find, if circumstances change, that they have moved from the safety of policy into the dock of criminal law.

VII. State Responsibility

Separate from individual criminal liability is the matter of state responsibility.

Under Article 16 of the International Law Commission’s Articles on State Responsibility, a state which aids or assists another state in the commission of an internationally wrongful act is itself internationally responsible if it does so with knowledge of the circumstances and if the act would be wrongful if committed by the assisting state itself.

This is not some obscure scholastic refinement. It is a plain rule. The United Kingdom cannot lawfully do through Washington what it is forbidden to do directly. If Britain would itself commit an internationally wrongful act by terror bombing civilian infrastructure in Iran, it cannot lawfully help the Americans do the same.

One might observe that this rule is honoured more often in the breach than in the observance. That does not make it unreal. It means only that the modern alliance system is held together by a common habit of pretending that legal responsibility evaporates in the presence of an American request.

VIII. Conclusion

If the United States were to attack civilian infrastructure in Iran that does not qualify as military objectives, or if it were to employ acts or threats of violence the primary purpose of which is to spread terror among the civilian population, such conduct would be prohibited by international humanitarian law. Where committed intentionally in the course of an international armed conflict, it would amount to war crimes. The legal position on that point is clear.

American leaders, ministers, generals, and individual servicemen may incur criminal responsibility in principle. The practical barriers to prosecution are political rather than legal. Great powers do not commonly escape liability because their conduct is innocent. They escape because they are powerful.

British ministers, officials, and servicemen stand on less secure ground. The United Kingdom has accepted treaty obligations, incorporated international crimes into domestic law, and bound itself to a legal framework from which American exceptionalism offers no shelter. If British bases or facilities are knowingly used to assist unlawful attacks on Iranian civilian infrastructure, the liability of those involved is not fanciful. It is real.

This, then, is the legal position. It is not complicated. What is complicated is the moral and political squalor that leads governments to speak as though the destruction of power stations and bridges were merely another tactic among many, and as though terror, when practised by a state with sufficient flags and lawyers, ceased to be terror.

It does not.

Reading List

The following works and instruments are the most useful starting points for anyone wishing to examine the legal framework in proper depth:

Primary Sources

1. Geneva Convention (IV) relative to the Protection of Civilian Persons in Time of War (1949).
2. Additional Protocol I to the Geneva Conventions (1977), especially Articles 48, 51, 52, and 54.
3. Rome Statute of the International Criminal Court (1998), especially Articles 8, 25, 27, 28, and 33.
4. International Criminal Court Act 2001 (UK).
5. International Law Commission, Articles on Responsibility of States for Internationally Wrongful Acts (2001), especially Article 16.
6. International Committee of the Red Cross, Customary International Humanitarian Law, Vol. I: Rules.

General Works on the Law of Armed Conflict
7. Yoram Dinstein, The Conduct of Hostilities under the Law of International Armed Conflict.
8. Marco Sassòli, International Humanitarian Law: Rules, Controversies, and Solutions to Problems Arising in Warfare.
9. Emily Crawford and Alison Pert, International Humanitarian Law.
10. Michael N. Schmitt (ed.), The Tallinn Manual 2.0 on the International Law Applicable to Cyber Operations — useful by analogy where infrastructure targeting is considered.

On War Crimes and Individual Responsibility
11. Antonio Cassese et al., Cassese’s International Criminal Law.
12. Gerhard Werle and Florian Jessberger, Principles of International Criminal Law.
13. William A. Schabas, An Introduction to the International Criminal Court.

On Aiding and Abetting, Complicity, and Command Responsibility
14. Kai Ambos, Treatise on International Criminal Law, Vol. I and II.
15. Ilias Bantekas, Principles of Direct and Superior Responsibility in International Humanitarian Law.
16. Neha Jain, Perpetrators and Accessories in International Criminal Law.

On the Protection of Civilians and Civilian Infrastructure
17. ICRC, Commentary on the First Geneva Convention and related updated commentaries.
18. Knut Dörmann, Elements of War Crimes under the Rome Statute of the International Criminal Court.
19. Reports and statements of the UN Special Rapporteurs and Commissions of Inquiry dealing with attacks on civilian infrastructure in recent conflicts.