War
Without
Rules

The Foundation: From Westphalia to the UN Charter

Modern international law governing armed conflict was not born in a moment of idealism. It was forged in blood. The Peace of Westphalia (1648) established the concept of sovereign states — the bedrock on which all subsequent international legal order was built. States agreed, in essence: your territory is yours; mine is mine; and we will not destroy each other without consequence.

The League of Nations (1919) attempted to codify this into collective security. It failed spectacularly. Then came the Second World War, and with it, the United Nations Charter (1945) — Article 2(4) of which contains perhaps the most important sentence in modern international law: "All Members shall refrain in their international relations from the threat or use of force against the territorial integrity or political independence of any state."

Article 51 provides the only recognised exception: the right to self-defence, individual or collective, when an armed attack occurs — and even that right is hedged, conditioned, and subject to the Security Council's oversight.

The Laws of Armed Conflict (LOAC) and International Humanitarian Law (IHL)

The Geneva Conventions of 1949 — four in number, with three Additional Protocols — constitute the spine of International Humanitarian Law. They govern how wars are fought: the treatment of prisoners of war, the protection of civilians, the rules around medical facilities and wounded combatants, and crucially, the obligations of attacking parties toward survivors.

Additional Protocol I (1977) extended protections to civilians in international armed conflicts and reinforced the principle of proportionality: military advantage must not be disproportionate to civilian harm. It also enshrined the duty of precaution — an attacker must do everything feasible to verify that targets are legitimate military objectives.

The Hague Conventions add another layer: rules on the means and methods of warfare. No poisoned weapons. No unnecessary suffering. No attacks on undefended locations. These are not aspirational ideals — they are binding treaty obligations on all signatories, which includes the United States, Israel, and Iran.

Was It Lawful to Strike the Iranian Frigate?

The answer hinges on several critical legal questions: Was there a formally declared or legally recognised state of armed conflict between the United States and Iran at the time of the strike? Was the frigate a legitimate military target? Was the attack proportionate? Was there a feasible alternative?

Under LOAC, warships of a belligerent state are legitimate military targets during armed conflict. However, the manner of the strike — without warning, in waters proximate to neutral states — raises immediate questions. The San Remo Manual on International Law Applicable to Armed Conflicts at Sea (1994), while not a binding treaty, represents customary international law and is applied by naval powers including the United States. It requires that attacks on naval vessels comply with the principles of distinction, military necessity, and proportionality.

Critically, Paragraph 47 of the San Remo Manual states that neutral waters — or waters in close proximity to neutral states — must be respected. An attack conducted in, or immediately adjacent to, Sri Lankan and Indian maritime zones without prior notification implicates the sovereignty and rights of those neutral nations.

The Geneva Convention Failure: Rescue and Notification

This is where the United States' conduct becomes legally indefensible — even under a war framework.

India and Sri Lanka, as uninvolved states whose exclusive economic zones and maritime interests were implicated, have standing to raise this before international bodies — including the International Tribunal for the Law of the Sea (ITLOS) and through the UN Convention on the Law of the Sea (UNCLOS).

Proxy Warfare and State Responsibility

Iran's use of Hezbollah, the Houthis, and other non-state proxies to wage indirect warfare is not new. What is new is the scale, the brazenness, and the geographic spread — from Lebanon to Yemen, from Gaza to Pakistan, from Bahrain to the streets of European cities.

Under the International Law Commission's Articles on Responsibility of States for Internationally Wrongful Acts (2001), a state bears responsibility for the conduct of non-state actors when it has effective control over those actors — the standard established by the ICJ in the landmark Nicaragua v. United States case (1986). Iran's degree of operational, financial, and logistical control over Hezbollah, in particular, has been extensively documented and meets this threshold.

When Hezbollah attacks civilian infrastructure in Israel, or incites violence in Bahrain and India, the legal responsibility does not stop at the non-state actor. It travels upstream to Tehran.

Attacks on European Territory: A New Rubicon

If Iran has, as alleged, moved to direct or proxy-facilitate attacks on European soil, it has crossed a threshold with seismic legal and political consequences. Under NATO's Article 5, an attack on one member is an attack on all — and if Iranian proxies are striking Germany, France, or any NATO member state, the entire alliance's collective defence architecture is activated.

More directly, attacks on civilian populations in European states constitute violations of customary international humanitarian law, regardless of whether a formal state of war exists. The prohibition on attacks targeting civilians — codified in Article 51, Additional Protocol I and recognised as jus cogens (peremptory norms from which no derogation is permitted) — applies in all circumstances. Jus cogens violations are not subject to sovereign immunity. They cannot be waived by treaty. They are the law that sits above all other law.

The Use of Civilians as Shields: The Gaza Dimension

Israel, backed by the United States, faces its own set of devastating legal questions. The prolonged siege of Gaza, the blockade of humanitarian aid, and the documented strikes on hospitals, schools, and refugee corridors have generated a growing body of evidence scrutinised by the International Court of Justice in proceedings brought by South Africa under the Genocide Convention.

Israel's position — that it targets military infrastructure within civilian areas because Hamas uses human shields — is a legal argument, not a legal absolution. The proportionality principle does not vanish simply because an adversary violates IHL. The obligation remains: a party to a conflict must do everything feasible to minimise civilian harm, even when the adversary makes that extraordinarily difficult.

The International Court of Justice (ICJ)

The ICJ is the principal judicial organ of the United Nations. It hears disputes between states and issues advisory opinions on legal questions referred to it by UN organs. South Africa's case against Israel under the Genocide Convention — filed in January 2024 and continuing through 2025 — is historic. Provisional measures were ordered, requiring Israel to take all measures within its power to prevent acts that could fall within the Genocide Convention.

Can the ICJ be similarly invoked against US or Iranian conduct? In principle, yes — subject to jurisdictional hurdles. Iran accepted ICJ jurisdiction in the 1955 Treaty of Amity with the United States. The US, however, withdrew its acceptance of compulsory ICJ jurisdiction in 1986, following Nicaragua. Voluntary submission, or specific treaty jurisdiction, would be required.

The International Criminal Court (ICC)

The ICC prosecutes individuals — not states — for genocide, crimes against humanity, war crimes, and the crime of aggression. Its jurisdiction is triggered either when the alleged crime occurs on the territory of a member state, or when the accused is a national of a member state.

The United States is not a party to the Rome Statute — and has actively threatened sanctions against ICC officials who investigate American nationals. Israel is also not a party, though Palestine's accession has extended ICC jurisdiction over conduct in Palestinian territory. In 2024, ICC Pre-Trial Chamber I authorised the Prosecutor to seek arrest warrants in relation to the situation in Gaza — a development with profound implications.

The UN Security Council: The Paralysed Giant

The Security Council holds primary responsibility for international peace and security. It can impose binding resolutions, authorise collective action, and refer situations to the ICC. But the veto power held by its five permanent members — including the United States — has rendered it effectively paralysed. This is not a failure of law. It is a failure of political will. The machinery exists. The legal authority exists. What does not exist is the political consensus among the powerful to deploy it.

Investor-State Disputes and Force Majeure

The billions of dollars in destroyed assets and destabilised investment portfolios represent not just an economic catastrophe but an emerging legal battlefield of their own. Investors — from infrastructure funds with exposure to Middle Eastern assets, to insurance syndicates underwriting maritime risk in the Red Sea and Indian Ocean — are now navigating a complex web of legal claims.

Bilateral Investment Treaties (BITs) typically provide investor protections including fair and equitable treatment, protection from expropriation, and access to international arbitration. Where state conduct — including military strikes on infrastructure, forced closure of airspace, or de facto seizure of assets — deprives investors of the value of their investments, BIT claims may arise.

Force majeure clauses in commercial contracts are being stress-tested at unprecedented scale. The question of whether 'act of war' exclusions in insurance policies cover state-on-state conflict versus non-state proxy attacks — or cover the attack on the Iranian frigate in waters that were not an official theatre of war — is currently generating litigation in London, Paris, Dubai, and Singapore.

Sanctions, Compliance, and the Weaponisation of Finance

The United States' deployment of secondary sanctions — penalising non-US entities that do business with Iran — has long been a source of legal friction. But in the context of active conflict, the stakes of sanctions non-compliance have escalated dramatically. Companies in India, the UAE, and Southeast Asia that maintained trade relationships with Iran before the conflict now face immense legal pressure.

The extraterritorial application of US sanctions is itself legally contested. Under principles of international law, a state's jurisdiction is generally limited to conduct within its territory, its nationals, and conduct directed against its state interests. Secondary sanctions — which penalise the nationals of entirely uninvolved third states for conduct entirely outside US territory — push hard against these boundaries. But the practical enforcement power of the US financial system means that 'legally contested' and 'practically avoided' are often the same thing.

India and Sri Lanka occupy a fascinating and deeply uncomfortable legal position. They are not parties to this conflict. Their waters were used — without permission or notification — as the theatre for a military attack. Their nationals may have witnessed or been endangered by the sinking of the Iranian frigate. Their coast guards were never called.

Under UNCLOS, coastal states have sovereignty over their territorial sea (12 nautical miles) and sovereign rights over their exclusive economic zone (200 nautical miles). Military activities within these zones by foreign states — without consent — implicate both treaty and customary law rights.

India, as a rising power with strategic interests across the Indian Ocean, has a legal basis and arguably a political interest to formally protest the US Navy's conduct through diplomatic channels, to seek clarification through ITLOS proceedings, and to demand that its maritime zones not become incidental battlegrounds for wars to which it is not a party.

The silence of neutral states in the face of such violations is not neutrality — it is acquiescence. And acquiescence, in the vocabulary of customary international law, matters. State practice and opinio juris — what states do and what they believe they are legally required to do — are the raw material from which customary law is built. If India and Sri Lanka say nothing, the US Navy's conduct edges closer to accepted practice.

The Erosion of the Rules-Based Order

Every time a powerful state commits a violation and faces no legal consequence, the rules-based international order contracts. Not because the law changes — it does not. But because the gap between the law's text and the law's enforcement widens, and that gap breeds both cynicism and imitation.

Smaller states watching the United States leave survivors in the Indian Ocean without rescue will draw conclusions. States watching Iran use proxies to evade direct attribution will take notes. The law is not destroyed. But its authority — which depends ultimately on states believing it will be applied to them — is being corroded.

The New Battlegrounds: Cyber, Space, and the Law's Edges

This conflict has already spilled into cyber warfare — attacks on critical infrastructure, communications networks, and financial systems. International law's application to cyber operations remains contested, under-codified, and urgently necessary. The Tallinn Manual 2.0, produced by NATO-affiliated scholars, attempts to map existing international law onto cyber operations — but it is not binding, and powerful states routinely deny its applicability to their own conduct.

If this conflict extends to attacks on satellites — communications, GPS, intelligence — it will trigger the Outer Space Treaty (1967) and push international law into territory it was never designed to govern at the speed required.

Accountability: The Long Game

History tells us that accountability in international law is slow, imperfect, and unequal. The Nuremberg Trials took years after the war ended. The ICTY and ICTR operated for decades. The ICC has been running for over two decades and has issued fewer than two dozen convictions.

But accountability does come. Evidence is being gathered — by journalists, by NGOs, by the UN Commission of Inquiry on Gaza, by national prosecutors in universal jurisdiction cases. The principle of universal jurisdiction allows states to prosecute war crimes and crimes against humanity regardless of where they occurred or the nationality of the perpetrator. Cases are being prepared in Spain, Belgium, and other states with robust universal jurisdiction laws.