International law can be used to diplomatically isolate the aggressor through formal legal determinations of wrongdoing, the suspension of international rights, and the pursuit of individual criminal accountability.
These mechanisms transform political condemnation into legally binding or authoritative consequences that undermine the aggressor’s legitimacy.
International bodies can issue authoritative rulings that label a state’s actions as an ‘act of aggression,’ which is defined as the use of armed force against the sovereignty, territorial integrity, or political independence of another state.
Under Article 39 of the UN Charter, the Security Council has the primary authority to determine the existence of an act of aggression and mandate measures to restore peace.
If the Security Council is deadlocked by a veto, the General Assembly can invoke the ‘Uniting for Peace’ resolution (377 A) to recommend collective measures, including diplomatic and economic sanctions.
States can bring disputes to the International Court of Justice to obtain a binding judgment that a war is illegal, effectively branding the aggressor a law-breaker in the eyes of the international community.
International law provides principles to limit an aggressor’s participation in the global community based on their breach of jus cogens (peremptory norms).
The UN and regional organizations can suspend or restrict the membership rights of states that flagrantly violate the UN Charter.
Legal principles like pacta sunt servanda (agreements must be kept) and bona fide (good faith) can be used to support the suspension of treaty-based benefits for an aggressor state.
States may legally withdraw diplomatic protection or expel diplomatic staff as a legitimate countermeasure against an internationally wrongful act.
Isolation is also achieved by targeting the leadership responsible for the aggression, rather than just the state as a whole.
The International Criminal Court (ICC) can prosecute individuals in senior political or military roles for the ‘crime of aggression’.
Domestic courts in any country can use the principle of universal jurisdiction to prosecute perpetrators of war crimes, crimes against humanity, or genocide, regardless of where the crimes occurred or the nationality of the offender.
The issuance of international arrest warrants severely restricts the ability of an aggressor’s leaders to travel or engage in international diplomacy, as treaty obligations may require other states to arrest them.
Laws regarding state immunity are being increasingly challenged to allow for the seizure of an aggressor state’s sovereign assets to pay for reparations.
States can legally implement travel bans and asset freezes against specific individuals linked to the aggression, further isolating the leadership from global financial and travel networks.
Groups like UNA-UK have stated that the US-Israeli strikes lack a legal mandate under the UN Charter and that the UK’s support undermines the international legal architecture. Human Rights Organisations have highlighted the devastating humanitarian impact, including reported strikes on civilian infrastructure like a girls’ school in Iran. Critics argue that by providing ‘defensive’ support, the UK is effectively complicit in these ‘illegal’ offensive operations. Amnesty International and Human Rights Watch have called for urgent diplomatic action and the use of ‘universal jurisdiction’ to investigate those responsible for human rights violations in Iran, while also urging the international community to protect civilians from the escalating conflict.
See – UNA-UK statement on the illegal and escalatory attacks on Iran – UNA-UK
‘The US and Israeli attacks on Iran, and the assassination of the country’s Supreme Leader, represent an illegal and unilateral war of choice. This act of aggression is a violation of the UN Charter and, along with Iran’s retaliation across the region, is fuelling a wider, growing conflict in which civilians again will pay the highest price.
The UN Secretary General has condemned the use of force by the US and Israel, as well as the retaliation by Iran across the region. Speaking to the UN Security Council, he said: “Military action carries the risk of igniting a chain of events that no one can control in the most volatile region of the world…Lasting peace can only be achieved through peaceful means, including genuine dialogue and negotiations.”
International law prohibits wars of aggression for good reason. The power and importance of these laws come from previous, bitter experience. The UN Charter was created by leaders who had lived through the Second World War and wanted to prevent future conflicts escalating into all-out, uncontrollable violence. They therefore agreed strict limits on the use of force, permitting it only in circumstances of necessary self-defence against an imminent threat.
The US and Israeli attacks on Iran do not meet this threshold. There has been no serious attempt by the US or Israel to make the international legal case that there was an imminent threat from Iran, and indeed US media are reporting Pentagon and Congressional sources saying there was none. No efforts have been made to convince the UN Security Council that the war is necessary, nor has President Trump sought approval from the US Congress’.