Since the United States and Israel launched their war against Iran, most international law experts appear to be speaking with one voice on the legality of the attacks.

Legal experts have said the attacks violated Article 2(4) of the UN Charter, which prohibits the use of force against states. The US and Israel have not produced any evidence that Iran posed an imminent threat to either of them. And neither has brought the matter to the UN Security Council. As such, this was a clear breach of international law.

But even though most scholars agree the strikes were unlawful, the public and political debate has shifted somewhere else entirely.

Instead of wrestling with the legal questions, many politicians, commentators, and everyday observers are counterbalancing the illegality with arguments about legitimacy.

Both Israeli Prime Minister Benjamin Netanyahu and US President Donald Trump have cast the war as a “necessary” fight between good and evil. Netanyahu said:

I know the cost of war. But I know sometimes that war is necessary to protect us from the people who will destroy us. […] We have to understand that we’re fighting here the bad guys. We’re the good guys. These people massacred their own people.

Canada and Australia, two of the US’ closest allies, have both used strikingly similar language in their statements about the war, saying they supported the US:

acting to prevent Iran from obtaining a nuclear weapon and to prevent its regime from further threatening international peace and security.

This idea of legitimacy – that is, what is “right”, “necessary”, or “just” – is now being thrown around in almost every conversation about the war.

Two arguments for a ‘just’ war

These arguments echo centuries‑old thinking about “just” wars.

Christian philosophers such as St Augustine (4th–5th century) and St Thomas Aquinas (13th century), for example, were early proponents of what is known as the “just war theory”. Basically, this means you
may violate the moral rule against violence if the cause is “just”.

In modern debates, arguments about the legitimacy of wars tend to fall into two categories.

The first claims attacks like the ones launched by the US and Israel are morally just and therefore ought to be permitted, regardless of what international law says.

This line of reasoning goes something like this: “So what if the action breaches international law? We removed an evil dictator.” Or: “Do we really want Iran developing nuclear weapons or long-range missiles?”

The statements by Netanyahu and Trump frame the use of force as morally necessary, implying that if an action feels righteous, legality should not be a hindrance.

The second argument dismisses international law altogether as ineffective or irrelevant.

The strand of legitimacy reasoning is also becoming common. It’s reflected in statements like: “Where was international law when people were being killed on the streets in Iran?” or “How can international law matter if Iran is constantly threatening western states and funding a proxy war?”

The conclusion drawn here is simple: if the law fails to prevent harm, it must be irrelevant. And if international law is irrelevant, then the US-Israeli strikes on Iran are legitimate.

Both of these lines of reasoning carry their own risks, not least the danger of allowing subjective morality to replace objective legal constraints.

Can a morally just war be deemed illegal?

The first argument hinges on the notion that the US and Israel strikes on Iran are just, given the brutal, repressive nature of the Iranian regime and the fact it is pursuing nuclear weapons. And international law should allow just actions.

But who decides what is just?

For the US and some of its allies, this is a binary moral equation: Iran is bad, we are good.

But this argument can also be made from Iran’s perspective: Israel and the US are bad. Therefore, we need nuclear weapons to protect ourselves.

Once states are permitted to act on their own sense of morality and justice, the international system goes down an extremely dangerous road. Every state can consider itself the “good” actor in its own story. If we allow individual morality to override the law, moral chaos follows.

Historically, moral arguments about “civilisation”, “enlightenment”, or “improvement” were also used to justify colonisation and slavery.

This is still happening in different contexts today: one group assumes its moral compass is universal, superior and mandatory for all others. If the world returns to that mode of thinking, the strongest states will once again become the arbiters of what counts as “good”.

International law must therefore remain objective, free from claims of moral exceptionalism.

Does international law still have relevance?

The second argument is even stranger: where was international law when a state like Iran committed atrocities?

This requires a clearer understanding of the role of international law. If we disregard international law because someone violates it, it’s like rejecting the rule book while still using its language to call out a foul.

Without it, there would be no norms to appeal to, no expectation of protection, no shared belief that certain harms are prohibited.

This argument also doesn’t follow logic. Murders still happen in countries like Australia. Should we therefore abandon domestic laws that prevent them?

Of course, there are double standards in international law. Powerful states have greater impunity and weaker states face more scrutiny.

But double standards also exist in domestic legal systems – wealthier people generally receive better outcomes than those with less means.

The existence of inequality in international law, then, shows the need for reform, not the abandonment of the law altogether.

Why this matters

The Iran war reveals a dangerous shift in the way states justify their actions: a growing preference for moral storytelling over legal reasoning.

Once the narrative of a “just war” replaces the rule of law, there is little left to restrain the powerful states from dominating the weaker ones.

The purpose of international law is not to determine who is morally good; it is to maintain order in a world where every state believes it is waging the “good” fight.