Prize Law Revisited: Between Permission and Regulation

[Pearce Clancy is a Research Fellow in Trinity College Dublin, funded by Research Ireland’s Postdoctoral Fellowship Programme]

2026 has not been a peaceful year. Armed conflicts continue to wage across the world, with a number of the most high-profile conflicts plunging the global economy into a state of crisis or otherwise posing direct threats to the rights of states not party to the conflict. More specifically, the re-emergence of blockades as a commonplace method of naval and economic warfare has put the historic tension between the rights of belligerent and neutral states back into the fore of international practice. The nearly 19-year-long Israeli blockade of Gaza, the Russian blockade of the Sea of Azov and the Black Sea, the US blockade of Venezuela, and now the US blockade and the Iranian closure of the Strait of Hormuz have reintroduced the law of blockade back into the mainstream of international law. With the exception of Israel, none of these states have established prize courts in connection with their respective blockades.

Although an obscure relic of the pre-Charter era today, prize courts were at one time seen as the most important part of the law of nations. Prize courts were judicial mechanisms embedded within domestic courts which had jurisdiction over declaring whether enemy or neutral vessels captured running blockades, transporting contraband, or providing ‘unneutral service’ could be condemned, thereby transferring title to the vessel to the capturing state. If the capture of the vessel adhered to relevant legal rules, chiefly those governing the law of neutrality, naval warfare, and any bilateral treaties applicable between the capturing and flag states, the vessel was deemed to be ‘good prize’. If these rules were not adhered to by the capturing state, the vessel should be released. Being embedded in the legal systems of each state, however, prize courts often applied differing interpretations of the law of nations, depending on the approach taken by their respective states and legal systems.

In this way prize courts served a dual function. They on one hand legitimised the exertion of belligerent rights over foreign vessels, giving the state judicial permission to formalise its seizure of the vessel in law. On the other, they provided a regulatory structure to this process. Prize courts provided some degree of protection for the rights of foreign vessels and allowed states and the masters of these vessels to demand these rights be adhered to. In theory, prize law served as a check against unrestrained belligerent rights.

Prize Law as Permission

It is open to serious question whether prize courts are appropriate today. In particular, it has been argued (see here and here) that the premise of prize law, that the private property of individuals can be forcibly seized and condemned, does not conform to legal developments since 1945, in particular the introduction of the prohibition on the use of force and the protection of private property in international human rights law. This is indeed a valid point—if the substantive law, in this instance the law of blockade, has been subject to a necessary revision in light of legal developments since World War II, then it stands to reason that the procedural law, i.e. prize law, ought to be similarly revised.

On top of the archaic nature of prize law, the example of the Israeli prize court, operating out of Haifa District Court, demonstrates a further issue. Applying an unorthodox and overly facilitative interpretation of the law of blockade, the Haifa court provides continued legal cover for what the International Court of Justice has deemed an unlawful occupation (see also UN General Assembly’s endorsement of the Court’s findings here). For a blockade to be lawful in international law, it must not be intended or have the effect of inflicting starvation or causing disproportionate harm to the civilian population, but also it must be the case that the methods used to enforce the blockade are lawful (San Remo Manual, Article 97). This can be described as a proportionality requirement in the law of blockade, the existence of which Israel rejects.

The Haifa court’s practice has been to accept the premise that the blockade is justified on grounds of security, without meaningful engagement with the ad bellum issues inherent to blockade as a use of force (see Definition of Aggression, Article 3(c), see also Wall Advisory Opinion, para. 139), or the apparent underlying intention and humanitarian consequences of the blockade, as required by customary international humanitarian law (ICRC Study, Rule 53, and San Remo Manual, Article 102). This has been the case since the court’s first prize case, concerning The Estelle.

Nor has the Haifa court given due consideration to the lawfulness of the means used by Israel to enforce its blockade of Gaza. It has recently declared some vessels which sailed as part of the 2025 effort of the Global Sumud Flotilla to breach the blockade as good prize and transferred ownership over the vessels to the state. This is despite credible evidence that the means used to enforced the blockade against the Flotilla were unlawful, including the alleged use of drones before interception and the mistreatment of detainees afterwards. More recently, Israeli Finance Minister Itamar Ben-Gvir has publicly released footage of the clear mistreatment of members of the Sumud Flotilla’s subsequent May 2026 attempt to much international condemnation by various heads of state.

The Haifa court’s proceedings regarding this more recent Flotilla will take time, however the court’s practice thus far has been to use prize law as legal permission to the state to continue the blockade, as well as providing judicial legitimacy to the state’s treatment and condemnation of those sailing on the Flotilla’s ships. Indeed, as was reported in 2010, following the attack on the Mavi Marmara (concerning which the Prosecutor of the ICC concluded there was a reasonable basis to believe involved the commission of war crimes) Israeli officials suggested that this ‘legal approach’ could be used as a punishment and deterrent for humanitarian blockade runners, rather than as a means of ensuring that state action is compliant with international law.

Prize Law as Regulation

If the use of prize law as permission poses difficult questions as to how to approach this body of law in the modern day, current US and Iranian practice pose equally difficult questions as to how to respond to the vacuum left behind where prize courts do not exist. Rather than make use of US courts’ prize jurisdiction, the US has opted, in its armed conflicts with Venezuela and Iran, to seize enemy and neutral oil tankers and institute forfeiture proceedings against them on the basis of unilateral US sanctions. The blockade issue is complicated by, first, questions over whether some of these vessels qualified as stateless, and second, that the US claims to have imposed a ‘global blockade’, rather than a geographically defined one, as required by international law (San Remo Manual, Article 94).

By bringing the issue under the remit of civil forfeiture, rather than the traditional law of prize, the US makes its own sanctions regime the relevant legal prism, rather than the law of blockade and the question of freedom of trade and navigation. Similarly, by arguing that such vessels were stateless—as in the case of the Russian registered Marinera—tricky issues regarding immunities could, if successful, be circumvented. It is not clear, however, that broader issues of the legality of the seizure under international law, or indeed the lawfulness of the US’s various blockades, would fit into civil forfeiture litigation. While sanctioned oil aboard stateless vessels may be legitimate for seizure through civil forfeiture under US law, the oil is not necessarily good prize under international law simply because it is aboard a stateless ship. Thus, by centring US legal mechanisms over international law, the regulative function of prize law is neutralised, and prize law’s balancing of the competing rights of states is discarded.

Iran, meanwhile, is imposing an increasingly complex system of restrictions in the Strait of Hormuz, most recently involving the creation of a ‘Controlled Maritime Zone’ where no vessels can enter without Iranian approval and the paying of tolls. Iran has accordingly seized a number of vessels in the Strait. Iran appears to be bringing seized vessels to port and detaining their crews. There has not been any statement (to the author’s knowledge) regarding prize proceedings being instituted, or the use of other mechanisms such as the US civil forfeiture.

The result of the lack of US and Iranian prize courts is that there is a stark lack of legal clarity on the future of these vessels, and—more importantly—on the continued restriction of trade through the Strait. The closure of the Strait by Iran, and its blockade by the US, is thus put beyond legal enforcement, thrust into a vacuum and grey zone left behind by the lack of contemporary prize courts, or indeed any replacement mechanism. While the regrettable permissive function of prize courts can be felt in Gaza, then, the consequences of the absence of their regulatory function can be felt in Hormuz.

Conclusion

The traditional law of blockade has been brought back into everyday international practice but largely without any of the oversight mechanisms that were developed in the pre-Charter era. Indeed, even where a prize court has been established, in Haifa, it has simply served to legitimise the exertion of belligerent state power, rather than meaningfully constrain or challenge it. In this way there is little functional difference between a permissive prize court and none at all, as in the current case of the US and Iran. There is as such no easy solution to this issue.

One possible, if highly unlikely, solution might be the creation of an International Prize Court, as was envisaged in an unadopted convention drafted at the second Hague Peace Conference in 1907. Given the reluctance of states to engage with prize law at the domestic level, it is unlikely they would suddenly agree to transfer prize jurisdiction to a new or even existing international court. Alternatively, although similarly unlikely and arguably undesirably, states could opt to construct and re-engage with domestic prize courts. This, however, comes with the risk of the co-option and weaponisation. Indeed, the use of prize courts has already been suggested within the context of the US-Iran war as a means of furthering the US war-effort.

Another option is simply to reject the notion that title can be transferred to belligerent states whatsoever, by any means. Do the legal rights of Israel, the US, and Iran to erect blockades (whether well-founded or not) trump the individual right to private property, the rights of the affected population, or the international community at large? There is an arguable case to say no, despite the historic doctrinal strength of belligerent rights. By this interpretation, neutral vessels attempting to run a blockade could be stopped but could not be condemned. Going a step further, it could be argued that blockade is no longer justifiable at all and should be discarded as a relic of a less humane version of international law.

Finally, there is room for the development of a new, standardised approach to the freedom of neutral trade, navigation, and blockade. It is not immediately clear what such an approach might entail. What is clear, however, is that the status quo of choosing between either the continued use of prize law as legal cover for unlawful blockades or the lack of any enforcement mechanism over the actions of blockading states is untenable.

Photo attribution: by Bruce Warrington on Unsplash