The Interception of the Madleen: Revisiting the Mavi Marmara Incident in 2025

[Konstantinos Deligiannis-Virvos is a PhD Research Fellow with the Norwegian Centre for the Law of the Sea (NCLOS) at the Law Faculty of The Arctic University of Norway (UiT)]

On 9 June 2025, the UK-flagged ship Madleen (officially the Barcarole), operated by the Freedom Flotilla Coalition, was intercepted by Israeli forces on the high seas, approximately 100nm from Gaza. Twelve activists onboard were arrested, and the ship, carrying small amounts of humanitarian aid, was taken to Ashdod. The mission aimed to provide limited relief to Gaza and – arguably mainly – to protest the actions of Israel against Palestinians. 

This interception is the latest in a series of similar incidents, the most (in)famous being the Mavi Marmara raid on 31 May 2010, which resulted in 9 civilian deaths (with one more later succumbing to injuries), several injuries, and 10 wounded Israeli soldiers. In this post I will investigate the parallels between the Madleen and Mavi Marmara incidents in order to investigate whether the actions of Israel against the Madleen were lawful under international law. Issues of human rights pertaining to the status of the crew and passengers of the Madleen are not discussed, even though important, since the focus is on the vessel. 

Law of the Sea and the Right of Visit 

The law of the sea grants flag States exclusive jurisdiction over their vessels on the high seas, with limited exceptions such as the right of hot pursuit (not applicable here) and the right of visit. Under Article 110 of the LOSC, except where acts of interference derive from powers conferred by treaty, a warship may only board a foreign-flagged vessel if there is reasonable suspicion of piracy, slave trade, unauthorized broadcasting, lack of nationality, or false flagging (p. 50-54).

As far as I am aware, there does not exist a bilateral or multilateral treaty that would allow the Israeli armed forces to interfere with the Madleen. It cannot be argued that the Madleen was engaged – or even willing to engage – in acts of piracy, slave trade or unauthorized broadcasting. As the ship is undoubtedly bearing the flag of the UK, the cases set in lit. (d) and (e) of LOSC Art. 110 are similarly not applicable. 

To date, Israel has not invoked Article 110 to justify its actions. Therefore, any legal basis for the interception must be examined under the law of armed conflict, specifically the legality of Israel’s ongoing naval blockade of Gaza under international law, as was the case with the Mavi Marmara.

The Naval Blockade of Gaza Strip 

Naval blockades are generally an accepted military tactic, the conduct of which is governed by the Geneva Conventions and customary international law expressed within the San Remo Manual on International Law Applicable to Armed Conflicts at Sea. After the Mavi Marmara incident, the legality of the blockade of Gaza was discussed in literature and in different enquiries of the incident. These enquiries were undertaken by Israel (Turkel Commission Report), Turkey (Turkish National Commission of Inquiry), the UN Secretary-General’s Panel of Inquiry (Palmer Report), the UN Human Rights Council (Fact Finding Mission Report), and the Office of the Prosecutor of the ICC (Report on the Situation on Registered Vessels). Due to space constraints, this post will not get into the details of each report (they are analysed in detail by Guilfoyle) but will highlight the main legal questions that are relevant for the Madleen incident and that were also raised after the Mavi Marmara incident.

A key question is whether the current conflict between Hamas and Israel, following the October 7 attacks, is an international armed conflict (IAC) or a non-international armed conflict (NIAC), as this determines Israel’s ability to impose a naval blockade on Gaza. While some, including the Turkel Commission (pp. 45–48) and the Palmer Commission (pp. 84–85), argue that naval blockades are permissible in both IACs and NIACs, this view is contested. State practice suggests blockades are limited to IACs (see Klein, p. 294, Guilfoyle, p. 179-181, Frostad, p. 200, and Heller).

Israel itself notes that the classification of the conflict is “a matter of debate” but claims its military operations adhere to the laws of armed conflict anyway. Israel’s Supreme Court, in the Targeted Killings Case (para. 18), classified the conflict with Hamas as an IAC.

De Hemptinne offered a detailed overview over the classification of the conflict between Israel and Hamas. I support the view that the current conflict is a NIAC under the 3^rd scenario described by De Hemptinne: that Palestine is a State and that Gaza is currently occupied, while Hamas is to be considered as a non-State actor. 

Without going into much detail, I argue that Palestine qualifies as a State, with a defined—though disputed—territory, a permanent population, governance by the Palestinian Authority, and recognition by 147 of 193 UN member states. It is also a non-member observer State in the UN and a party to several international conventions. 

Moreover, especially since the October 7 attacks it is argued that Gaza is occupied by Israel. Israel argues that this situation changed in 2005, when Israel “disengaged” from Gaza (a view supported here). This could be argued more easily during the Mavi Marmara incident (p. 82) but in 2025 at the time of the Madleen incident, Israel is arguably the occupying power, recognised recently by UNGA in A/ES-10/L.34/Rev.1. 

Finally, Hamas is to be considered a non-state actor because it is not recognized as the government of Palestine, in contrast with the Palestinian Authority led by Fatah. The fact that Hamas controls Gaza and enjoys the support of a significant percentage of the Palestinian population does not automatically establish it as a state actor (see also Guilfoyle, who did not consider Palestine a State). 

Thus the current conflict is a NIAC, or that a NIAC and an IAC are running parallel, as the ICC Prosecutor suggested. In any case, the naval blockade under which the Madleen was intercepted was part of the NIAC between Israel and Hamas: the current blockade of Gaza, including the naval blockade, officially started on March 1 since the Israeli government maintained that sufficient humanitarian aid entered the Gaza strip during a 6 week ceasefire with Hamas. According to the Israeli Government, the blockade is also part of the mounting pressure upon Hamas to release hostages after the October 7 attacks. Consequently, the naval blockade is illegal since it is not permitted to impose a naval blockade during a NIAC and thus the interception of the Madleen was illegal as well. The same view was supported by Guilfoyle, regarding the Mavi Marmara incident, a view supported by Turkey.

What if Naval Blockades are Legal During NIACs?  

It could be argued that the naval blockade was legally imposed, a view supported by the Turkel and Palmer Reports. Guilfoyle (p. 194-207) also explored this possibility in the context of the Mavi Marmara incident. While I will not revisit that discussion in detail, it is important to highlight certain key differences between the 2010 blockade and the current incident.

The first difference relates to the intensity of the conflicts in 2010 and 2025. Guilfoyle (p. 179) highlighted that for a conflict to qualify as a NIAC, it must meet the “protracted armed violence” criterion set out in Prosecutor v Tadić, para. 70, which can be a question of intensity more than duration. In 2025, the situation is arguably one of protracted armed violence: both the October 7 attacks by Hamas and the then operations of Israel in Palestine are far more intense than in 2010. 

Secondly, Guilfoyle (p. 213-215) argued that if the Mavi Marmara blockade was lawful, civilians onboard would still be protected under Common Article 3 of the Geneva Conventions, applicable in both IACs and NIACs. In contrast, the treatment of the 12 activists aboard the Madleen differed significantly. Unlike the Mavi Marmara, no excessive violence or human casualties were reported during the Madleen incident, and the activists were not subjected to similar levels of force during the interception.

Finally, assuming Israel’s naval blockade is lawful, there is need to examine its impact on Gaza’s population, especially considering the recent ICJ Orders in South Africa v. Israel. As the San Remo Manual states in para. 103(b) 

[…] the blockading party must provide for free passage of such foodstuffs and other essential supplies, subject to: […] the condition that the distribution of such supplies shall be made under the local supervision of a humanitarian organization which offers guarantees of impartiality […]. 

The State of Israel official Twitter/X account described the vessel as a “selfie” or “pleasure yacht” and never alluded to it carrying weapons or other contraband goods and noted that “The tiny amount of aid that wasn’t consumed by the “celebrities” will be transferred to Gaza through real humanitarian channels”, undoubtedly hinting that the San Remo Manual para. 103(b) is followed.

However, para. 102 notes that “the declaration or establishment of a blockade is prohibited if: (a) it has the sole purpose of starving the civilian population or denying it other objects essential for its survival; or (b) the damage to the civilian population is, or may be expected to be, excessive in relation to the concrete and direct military advantage anticipated from the blockade”. The UN Human Rights Council Fact Finding Mission Report (para. 52-53) found that the blockade that led to the interception of the Mavi Marmara was illegal under this rule, a view also shared by Guilfoyle.

A question that arises in this instant is whether the naval blockade of the Gaza Strip is a continuous one since 2007 (or later) or whether it is a series of blockades, each one with a distinct time frame, and the most recent one being the one that was imposed on 1^st March 2025. It can be argued that since the October 7 attacks a new armed conflict has emerged between Israel and Hamas which has not ended until the day of the Madleen incident, and thus the current blockade has to be judged on its own merit. 

Today, this can be discussed under the light of the recent preliminary measures in the Application of the Convention on the Prevention and Punishment of the Crime of Genocide in the Gaza Strip (South Africa v. Israel). In the Order of 26 January 2024 the Court noted the urgent need for basic services and humanitarian assistance due to the dire conditions in Gaza and instructed Israel to “take immediate and effective measures to enable the provision of urgently needed basic services and humanitarian assistance to address the adverse conditions of life faced by Palestinians in the Gaza Strip” (para. 80). In the subsequent Order of 28 March 2024 the Court recognized that the humanitarian situation had “deteriorated further” since the January order (para. 18) and in the 24 May 2024 Order it observed that the “catastrophic humanitarian situation” had “deteriorated, and has done so even further since the Court adopted its Order of 28 March 2024” (para. 28). 

Even if the Orders do not refer to the naval blockade itself, it is safe to assume that they cover every corridor that may provide humanitarian aid, including through the sea. The humanitarian aid that could be provided for by sea corridors would arguably not be more significant than aid coming from land (noted in the 28 March Order, para. 35), but the provisional measures do not specify land crossings as opposed to sea (or air) crossings but only highlight their increased importance. Before suggesting that Israel follows para. 103(b) of the San Remo Manual, the effects of the blockade upon the population have rendered it illegal. Due to the urgent need for aid the maintenance of the naval blockade (even if it was considered legal, which is dubious) is contradictory to the ICJ Orders, which are binding on Israel.

Photo attribution: “Mavi Marmara leaving port” by Free Gaza Movement is licensed under CC BY-SA 2.0