Mustafa TUNCER, Assistant Professor of International Law at the Naval War College of the Turkish National Defence University.[1]
On 9 June 2025, the Israeli Navy boarded and captured the Madleen, a British-flagged activist vessel carrying humanitarian aid to the Gaza Strip, as part of the enforcement of the naval blockade declared in 2009. This incident, along with the earlier “unidentified” drone attack in May against the Conscience, a similar activist vessel bound for the Gaza Strip, once again drew international attention to the ongoing Gaza blockade, 15 years after the attack against the Mavi Marmara, which resulted in the death of 10 civilians on board.
Although the Mavi Marmara attack triggered broad discussion in international legal scholarship on the legality of the Israeli blockade of the Gaza Strip, the debate did not address the question of whether the Israeli control exercised over this territory constitutes an obstacle to the establishment and enforcement of a naval blockade. This issue has gained importance after 7 October 2023, when the Israeli Defence Forces (IDF) launched a full-scale operation, including a physical military presence on the blockaded coastline and broader control over the Gaza Strip.
This analysis consists of two main parts. The first examines the raison d’être of naval blockades, with a particular focus on their relationship with military occupation. The second enquires whether international humanitarian law considers Israel as the Occupying Power in the Gaza Strip, in light of the factual situation since 7 October 2023. Based on the findings in these two parts, this study argues that, among other reasons rendering the Gaza blockade unlawful, Israel cannot maintain its naval blockade, since its status as Occupying Power precludes it from establishing and enforcing such a blockade.
(In)Compatibility Between Military Occupation and Naval Blockade
Regarding the question whether an occupied territory may be subjected to a naval blockade, one of the earliest arguments was put forward by the Turkish Report on the attack against the Mavi Marmara, which asserted that ‘a State cannot, by definition, blockade the borders of territory it occupies.’ In response, Longobardo criticised the Turkish Report for not providing ‘a sound argument to support this view’, and argued that the law of blockade and the law of occupation are distinct legal regimes, which could therefore coexist during a naval blockade of an occupied coastline. Guilfoyle, meanwhile, presented a more ambiguous perspective and highlighted the silence of some expert manuals and national military manuals, particularly the 1994 San Remo Manual, which is regarded in the literature ‘as an authoritative statement of existing law’.
It is true that the rules of the San Remo Manual on naval blockades do not exclude the possibility of a belligerent establishing a blockade of a coastline under its occupation. More importantly, however, they do not suggest that it is permissible either. The silence of the San Remo Manual should be examined in conjunction with other sources to determine whether such a customary rule exists in the law of naval warfare.
The 1909 London Declaration and the 1913 Oxford Manual, both considered to reflect the customary rules of their time, restricted the geographical scope of naval blockades to ‘ports and coasts belonging to or occupied by the enemy.’ These historical sources clearly demonstrate that the burden of proof lies with those who argue that the customary rules on blockades have since evolved to permit blockades of occupied territories.
Nevertheless, there is no evidence that State practice has extended naval blockades to occupied coastlines. Apart from a few national military manuals that reiterate the silence of the San Remo Manual, several national manuals, such as the 2006 German Manual (para. 1060), the 2006 Australian Manual (para. 6.60), and the 2022 U.S. Commander’s Handbook on the Law of Naval Operations (para. 7.7.1), explicitly state that blockades may be imposed only against ‘ports … or coastal areas belonging to, occupied by, or under the control of an enemy State’.
Finally, the 2023 Newport Manual (para. 7.4.1), along with its second edition of 2025, ‘a purely lex lata exercise’ prepared by some of the most renowned scholars of the law of naval warfare, confined the scope of a blockade to ‘specified coastal areas that are under the sovereignty, occupation or control of an enemy.’
This position is a direct consequence of the historical evolution and rationale of naval blockades, a method of warfare that emerged as the maritime equivalent of sieges. The analogy between sieges and blockades is not merely historical but remains relevant today. For example, the 2022 French Manual (para. 5.5.4), assessed these two methods of warfare under the same category, thereby rendering the establishment of a naval blockade of an occupied coastline impossible. Accordingly, just as an occupied territory cannot be besieged by its Occupying Power, an occupied coastline cannot be blockaded by its Occupying Power, since blockades, by their nature, aim to interrupt maritime navigation to and from a portion of coastline under the control of the adversary.
This does not mean, however, that the Occupying Power cannot implement certain measures at sea to ensure the security of its effective control over the occupied coastline. For example, it may, in exceptional cases, suspend the innocent passage of foreign ships through the occupied territorial sea under Article 19(2) of UNCLOS, or establish a ‘maritime exclusion zone’ in an area near to the occupied territory (paragraphs 105-108 of the San Remo Manual). Although such measures may resemble naval blockades in practice, they are based on entirely distinct legal foundations and do not confer the same broad authority to restrict maritime navigation as naval blockades.
Is Israel an Occupying Power in the Gaza Strip?
The legal status of the Gaza Strip under the law of occupation has been controversial since the establishment of the naval blockade in 2009 and the accompanying land crossings policy, which imposed a total suspension of the movement of people and goods to and from the Gaza Strip. As noted above, following the Mavi Marmara incident, the 2010 Turkish Report asserted that Israel, due to its combined control over the Gaza Strip, became an Occupying Power. In response, the Israeli Report (also known as the Turkel Commission Report) rejected this view, and argued that the Israeli occupation of the Gaza Strip ended in 2005 with the withdrawal of Israeli troops therefrom (paras. 45-47). Since then, the Israeli position has remained unchanged, as reflected in a recent decision of the Israeli High Court of Justice.
Prior to 7 October 2023, several actors in the international community, such as the UNHCHR, the UN OCHA, the ICRC, the EU and the UK, expressly supported the view that Israel retained its status as the Occupying Power in the Gaza Strip. Following this date, the ICJ, in its Advisory Opinion of 19 July 2024, affirmed this position, stating that ‘Israel remained capable of exercising, and continued to exercise, certain key elements of authority over the Gaza Strip … despite the withdrawal of its military presence in 2005. This is even more so since 7 October 2023.’ Similarly, among others, the ICRC the UN HRC, and the UK, the flag State of the Madleen, reiterated their previous position regarding Israel’s status as the Occupying Power in Gaza.
In addition to the controversy over Israel’s indirect effective control over the Gaza Strip, the factual situation has clearly changed since 7 October 2023, with increased Israeli control on the ground. The IDF became present in most of the Gaza Strip within a short time. This presence also extended to the coastline, under blockade since 2009, including the Port of Gaza, captured on 16 November 2023, and about half of the coastline, controlled during different phases of the Israeli operation (see here, and here). According to Israeli sources, the IDF controls over 50% of the Gaza Strip, and aims to increase this to 75%. These facts provide sufficient evidence even for those who support the ‘boots on the ground’ requirement to recognise the existence of an occupation.
Conclusion
As a result of the incompatibility between the law of blockade and the law of occupation, Israel is not legally permitted to impose a blockade as long as it remains the Occupying Power in the Gaza Strip. Therefore, the current naval blockade, in effect since 3 January 2009, is unlawful, among other reasons, due to the continuing Israeli occupation. This occupation has either existed from the outset of the blockade, through ‘indirect effective control’, or since 7 October 2023, through the fulfilment of the ‘boots on the ground’ requirement. This analysis supports the former view, and thus considers the Gaza blockade to have been void ab initio. In either case, it must be emphasised that international humanitarian law does not permit belligerents to create legal loopholes to avoid offering meaningful protection to those affected by hostilities. Accordingly, in relation to the Gaza Strip, Israel must respect its obligations under the Fourth Geneva Convention as the Occupying Power and end its blockade of the coastline, including the Port of Gaza, which is already under its control.
[1] Any views and opinions presented in this post are solely those of the author and are expressed exclusively in the author’s personal capacity.
International Law Blog 
This is a thought-provoking analysis of international law concepts such as law of occupation, blockade and siege among others. International and even municipal law, however, cannot be looked at in isolation. Kelsen’s pure theory of law does not adequately explain so many ‘legal’ problems that perpetuate injustice around the world. Therefore, it may be prudent to recall how E H Carr analysed international law. Carr’s mind was exercised a lot by the question of the limitations of international law. Carr dismissed the idea of law and international law as independent and more important than politics. He questioned the premise that by establishing the rule of law and maintaining international law and order we “transfer our differences from the turbulent political atmosphere of self-interest to the purer, serener air of impartial justice” (Carr 2016, 159). This is an erroneous assumption because it presumes that the stages of development or maturity of international law and municipal law are at the same level. Carr argued that international law lacked an executive, legislature, and judicature -three main institutions – which are essential parts of developed systems of domestic law: In the international realm, there are neither agents to enforce law nor courts that can render decisions that are recognised as binding by all members of the international community. Custom (state practice and opinio juris) is the only source of law, rather than direct legislation. This results in international law being a PRIMITIVE type of law—the law of an undeveloped rather than a fully integrated community (Carr 2016, 159-160). Morgenthau held that international legal rules are either the result of efforts to overlook prevalent dissension through agreements on superficial verbal formulae that either seek to maintain the status quo or merely design procedural devices that may be used to resolve conflicts through compromise (Morgenthau 1953, 143-144). So, law does not always provide justice to victims of injustice. In other words, the ground reality of geo-strategic, political, economic, scientific, technological and socio-cultural attributes that help sustain such conflicts cannot be altogether glossed over.
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