You have argued that the traditional belligerent right to seize enemy or neutral property at sea sits uneasily with States’ obligations under the Charter of the United Nations [UN Charter]. Is it possible to reconcile prize law with the Charter’s collective security framework? Should the legality of a State’s resort to force determine whether prize measures can be taken at all?

Indeed, to make the point, I have argued that it makes no sense for everyone to agree that it is completely forbidden for a State to violate the UN Charter by launching an attack and engaging in naval warfare with another State, and then in the same breath to agree that the State which resorts to aggression can then have the so-called “belligerent right” to seize enemy merchant vessels and airplanes and keep them as acquired property forever, under prize law.

This argument elicits two responses. First, the critics will say, “But this is war! You can’t apply peacetime logic to wartime!” And second, they tell me that I am mixing up two separate branches of international law – jus ad bellum and jus in bello – and that we all know that it is impossible to agree on who was the aggressor; both sides will claim self-defence. The successful application of the laws of war, they say, is built on always keeping these two branches separate. But my response to this is: first, perhaps we should be applying some peacetime morality – why should we venerate war? And second, let us agree that neither the aggressor nor the victim can keep the enemy ships and cargo. The idea that being “at war” gives you belligerent rights to seize and keep things should indeed be seen as a relic from a bygone era. So, I am not suggesting that it is only the aggressor State that is prevented from seizing ships as prize; we should agree that neither State has a so-called “belligerent right” to seize enemy ships as prize. I am suggesting that no State has the right to seize and keep things that do not belong to it. We do not prohibit burglary and then say, “But once the burglar starts, they can keep whatever they manage to steal!” Nor do we say, “The victim can react and go and capture whatever belongs to the attacker.” Nobody has the right to steal things that do not belong to them. States should not consider that just because they are engaged in naval warfare, they can forcibly acquire private property at sea belonging to their enemies.

This leaves your question about collective security. In addition to the possibility that a State’s use of force in self-defence could be legal under the UN Charter, it is possible that the use of force has been authorized under the Charter’s collective security framework. I have thought about this a bit and looked at some practice. In the end, even if the use of force is authorized by the UN or is carried out as part of a UN operation with blue helmets, I don’t believe either the States so authorized or the UN itself should be acquiring ships and cargo on the high seas by invoking prize law. The era of “legalized piracy” should be considered over.

Classic prize law attempted to balance the belligerent States’ interest in weakening their enemy with the neutral States’ right to continue trade with the belligerent States. In contemporary international armed conflicts, often involving sanctions regimes and global supply chains, does this balance remain viable? How should modern law protect neutral shipping?

I think this idea of balancing reveals the heart of the problem. It admits that the law should protect the interests of States that have gone to war against the interests of others who have nothing to do with the war. But the era when States could choose to go to war is over as per the rules of the UN Charter, and those States that choose to go to war should not be determining how the rest of the world protects its belligerent interests. And of course, as you suggest, who knows exactly what sort of goods and nationality are actually characterizing massive container ships with thousands of containers? It has already been pointed out in this Review that enforcing the law of contraband against neutral shipping through prize courts would be “difficult to imagine” in this modern context.Footnote ¹ Of course, a State acting in self-defence does have legitimate interests. How can these interests be protected vis-à-vis neutral shipping? The answer under international law, I would suggest, must be: by allowing the defending State to interfere with that neutral shipping, for example by looking for arms destined for the aggressive State, to the extent that this is proportionate and necessary at the time for the defending State’s self-defence.Footnote ²

Today, private enemy property on land is generally protected from confiscation due to the rule prohibiting pillage – yet maritime capture of private vessels and cargo has historically been treated differently. Is there still a principled legal distinction between land and sea in this regard, or should civilian property enjoy equivalent protection in both domains? Should there be a normative difference between enemy and neutral private property on land and at sea?

I agree that property at sea has historically been treated differently from private property on land. I don’t see a principled reason for such a legal distinction. The distinction is justified, by those who choose to justify it, on the grounds that private property on land in wartime is protected by treaty, whereas property at sea has been historically seized as prize and the law has not outlawed this yet by treaty. But I can’t see that domain-specific exception as a principled distinction. So, to answer your question, no, I don’t think there should be a distinction, and to be clear, I would keep the protection of enemy and neutral private property as a matter of humanitarian law both on land and at sea – and elsewhere, such as in outer space, where some would like to see prize law applied.

Prize law traditionally relied on specialized prize courts to adjudicate captures before property title could pass on to the captor State. In the contemporary landscape, where such courts are rare and international tribunals are more prominent, how should captured vessels and cargo be reviewed? Is there a case for reviving prize courts, internationalizing them, or abandoning the system altogether?

I suppose by now it will come as no surprise that I consider there to be absolutely no case for reviving national prize courts. The idea or operationalization of an international prize court would confirm for everyone that international law is made by powerful States so that they can steal from weaker States and their citizens through aggression and superior military force at sea. An international prize court would bring the full authority of international law to confirm that title to ships, planes and goods had passed from those deemed to be enemies or neutrals to the State capable of capturing those privately owned assets through its military muscle. If one were looking for another incentive to go to war, reinforcing the idea of prize law could only provide a bizarre incentive for States with powerful navies. It would be very lucrative – it’s not known as prize law for nothing!

You have written on the law of naval warfare and publicly called for its re-evaluation, and you’ve also offered concrete suggestions in this regard in the naval warfare workstream of the International Committee of the Red Cross [ICRC] Global Initiative on IHL. Could you tell us why you have made such a call and explain the rationale of your suggestions?

The Global Initiative on IHL presents a very timely opportunity to discuss multiple issues, including the humanitarian protection that needs to be ensured in the context of naval warfare. My suggestions in the naval warfare workstream in 2025,Footnote ³ and my detailed writings on blockade,Footnote ⁴ argue that the time has come to revise the manuals and to make it clear that States should not be able to acquire private property on the high seas through any application of prize law (should it still exist). My rationale is that, first, the continuing assertion in the manuals that this is good international law, and part of the law of naval warfare, means that all kinds of ships can be boarded, seized, captured, condemned, targeted and destroyed, as part of a continuing logic that all ships and goods on board can potentially benefit the enemy. And second, by imagining enemy merchant and other shipping this way and carving out exceptions for war at sea, States are endangering the civilian passengers and crew more generally. We might also recall the enduring rule in Article 4(A)(5) of Geneva Convention III that the crew (including apprentices) from a merchant ship of a party to the conflict can be interned as prisoners of war until the end of the conflict.Footnote ⁵

Looking forward, do you believe prize law should be reformed, codified anew, or abolished? At a time when the international community is revisiting the law of naval warfare, what principles and values should guide such a task?

I hope it is clear that I don’t consider that prize law should be tinkered with, let alone codified. Rather than framing my approach as abolitionist, I would prefer to argue that, to use your expression, prize law is “a relic from an earlier era” and can no longer be applied as good law. Yes, the King of England may have relied on this body of law to decide that the capture of a Portuguese ship and its cargo was “good prize” as far back as 1357. The British, French and others may have established national prize courts and case law over the years to adjudicate and validate as a matter of international law such captures in wartime.Footnote ⁶ However, just because something has existed as a legal institution for a long time does not mean that it remains morally acceptable – think of slavery, for instance. The whole point of the UN Charter and the subsequent evolution of the UN is to prevent States from going to war; to allow that today they can be rewarded with prize makes no sense. As for the victim State in a war, there are other ways to award reparations than sanctioning the capture of whatever the victim manages to seize from the other side.

The values that ought to guide us are front and centre in the Global IHL Initiative, which is prominently branded across all sites as “Humanity in War”. There must be a desire to ensure that our humanity is protected and that all people are treated with consideration for their dignity. This means not just reiterating interpretations of the law of naval warfare, based on nothing more than the idea that this law cannot be tampered with because that is how it was applied for centuries. We should recognize that in those days, powerful naval States made the rules to suit their wartime interests; all States should today ask whether the idea of belligerent rights at sea said to flow from prize law still represents good international law.

The Global IHL Initiative states: “Any armed conflict must be fought with a plan for an eventual peace.”Footnote ⁷ Continuing with the idea that being in an armed conflict entitles States to acquire as prize enemy ships and cargo seized on the high seas hardly seems conducive to a future peace. The Global IHL Initiative also states that we stand for a future where the laws of war are “the foundation of our shared humanity”.Footnote ⁸ Rules which authorize the targeting of merchant ships should they resist seizure as prize, and allow for interning certain members of their civilian crew as prisoners of war, seem to be unsuitable for inclusion in the foundations of our shared humanity.