At 2.30am EST on Saturday morning, President Donald Trump announced via a video on Truth Social from his resort in Mar-a-Lago that the U.S. military has begun “major combat operations in Iran.” The overnight strikes, which are an unequivocal violation of the UN Charter, come after weeks of U.S. military build-up in the region and against the backdrop of ongoing diplomatic negotiations over Iran’s nuclear program.
At 4pm this afternoon, the UN Security Council (UNSC) will convene in an emergency session to address the crisis. We can expect to hear condemnations from U.S. adversaries, several of which will be hypocritical and performative. It is the behavior of traditional U.S. allies however, and in particular permanent UNSC members the United Kingdom and France, that matters most. Their positioning will be a harbinger of whether the legal cornerstone of the current international order that is designed to maintain, as best as possible, world peace can hold.
In the aftermath of World War II, Article 2(4) of the UN Charter solidified a major shift in understanding about how nation states should interact. In earlier times, using force for political or territorial conquests was commonplace. As Oona Hathway and Scott Shapiro frame it: “The outbreak of war did not constitute a breakdown of the international order—it was the order.”
Article 2(4) pursued a new path, prohibiting the “threat or use of force against the territorial integrity or political independence of any State.” UN Member States continued to have the full range of non-military options to pursue their interests, and in the UN Charter era we have seen States using economic sanctions, travel bans, and an array of other coercive tools (from overflight denials to non-forcible cyber measures) to influence the behavior of States they feel threatened by. But the use of military force no longer has a lawful place in that toolkit.
There are, of course, two carefully crafted exceptions to this prohibition – one for self-defense in the face of an actual or imminent armed attack, and the other for actions taken through the UN Security Council to maintain or restore international peace and security. As Mike Schmitt, Tess Bridgeman, and Ryan Goodman explained last week in Just Security (and as Marko Milanovic reiterated after the strikes began this morning), neither of these are met in the current situation, and it is not a close case.
The challenge facing the United Nations this afternoon is not about the interpretation of international law. The U.S. military attack on Iran is a textbook example of a manifest violation of Article 2(4). The challenge is a political, economic, and – fundamentally – ethical one. States including the U.K, France, Germany, Australia, and Canada have spent decades espousing their commitment to international law. As recently as this week, each of these countries voted in support of a UN General Assembly resolution supporting Ukraine in the face of Russia’s violation of Article 2(4), which they have each, rightly, condemned.
This afternoon, these States must ask themselves whether the international legal order protects the sovereignty of everyone in the international system, or only the sovereignty of like-minded States. Does their willingness to condemn violations of Article 2(4) extend to everyone, or only to their adversaries (or, alternatively, those with minimal ability to harm their national interests)?
It is important not to be cavalier about the scale of the challenge facing these traditional U.S. allies as they figure out how to respond to a system in which the United States no longer seems interested in paying even lip service to international law. In the living memory of all the politicians, diplomats and lawyers of these governments, the United States has wanted to present itself in compliance with international law, even amidst the many instances in which it has, in fact, breached the law. The Trump administration’s second term marks a clear break from that approach.
If the recent past provides any prologue, the indicators are poor. This afternoon’s meeting had a dress rehearsal in June 2025, after a series of military attacks on Iran by Israel, and then the United States. At that meeting, the U.K. tried to speak from both sides of its mouth, noting that the U.K. did not participate in the strikes, while carefully avoiding any characterization of the strikes as unlawful:
“We have long made clear that Iran must not have a nuclear weapon and that its nuclear programme represents a serious threat to international peace and security. The United States took action last night to alleviate that threat. The United Kingdom did not participate in United States or Israeli strikes.”
So far today, the U.K. and other erstwhile supporters of the UN Charter have made statements along similar lines. In a joint statement by the U.K., France and Germany, the States’ leaders distance themselves from what they clearly know is unlawful U.S. military action, while refraining from condemning it:
“We did not participate in these strikes, but are in close contact with our international partners, including the United States, Israel, and partners in the region. We reiterate our commitment to regional stability and to the protection of civilian life.”
Canada, meanwhile, has placed itself into alignment with U.S. actions. In a statement issued on X, Prime Minister Carney stated:
“Canada supports the United States in acting to prevent Iran from obtaining a nuclear weapon and to prevent its regime from further threatening international peace and security.”
The statement is an embarrassing about-face following the prime minister’s speech entitled, ““Principled and Pragmatic: Canada’s Path,” presented in Davos earlier this year.
Australia’s Prime Minister, Anthony Albanese, made a remarkably similar statement:
“We support the United States acting to prevent Iran from obtaining a nuclear weapon and to prevent Iran continuing to threaten international peace and security.”
In the face of Trump’s wide-ranging threats and actions against any who oppose him (tariffs, territorial seizure, invasion and leadership abduction), it is hardly surprising that States like Canada might pull their punches. And for the European Union, with an aggressive Russia on its doorstep and a defense system that will take many years to wean itself off U.S. dependency, the costs of standing up for the UN Charter at this moment are high.
The trouble is, the long-term cost of giving up on Art 2(4) of the UN Charter may be even higher.
The post International Reactions to Military Strikes on Iran: A Tipping Point for the UN Charter? appeared first on Just Security.
Great Job Rebecca Hamilton & the Team @ Just Security for sharing this story.
