Ali Fuat KuzThe starting point is simple. International law recognises the high seas as a space beyond the jurisdiction of any single state.
Under both customary law and the United Nations Convention on the Law of the Sea (UNCLOS), ships navigating on the high seas are subject solely to the authority of their flag state.
To attack such a ship is to attack the sovereignty of the flag state itself. The Sumud vessels were well outside Israel’s twelve-mile territorial sea.
Israel, therefore, had no lawful jurisdiction to intercept them.
Israel's primary legal defence for its actions on the high seas is the enforcement of a maritime blockade against Gaza.
However, this justification collapses under scrutiny, as the blockade itself is fundamentally illegal under established principles of international humanitarian law.
It is inseparably linked to an occupation declared unlawful by the International Court of Justice.
The San Remo rules are regarded as an authoritative restatement of customary international humanitarian law and have indeed been invoked by Israel itself to justify its illegal blockade, outlining strict conditions for a lawful maritime blockade.
For a blockade to be valid, it should be applied as a measure of warfare and is therefore inherently temporary, justified only by military necessity for the duration of active hostilities.
Israel's maritime blockade of Gaza, formally imposed in January 2009, has been in continuous effect for over 16 years.
Its indefinite and long-term nature is fundamentally incompatible with the legal requirement that a blockade be a temporary measure tied to a specific armed conflict.
It has transformed from a wartime tactic into a permanent feature of control, which removes it from the legal framework of a legitimate blockade.
Furthermore, the San Remo Manual explicitly prohibits a blockade if it has "the sole purpose of starving the civilian population or denying it other objects essential for its survival" or if "the damage to the civilian population is, or may be expected to be, excessive in relation to the concrete and direct military advantage anticipated".
The law goes further, creating a positive obligation.
If the civilian population of a blockaded territory is inadequately supplied with essentials, the blockading party must provide for the "free passage" of such foodstuffs and supplies.
The passage of medical supplies is not discretionary; it shall be allowed.
The Gaza Sumud Flotilla was a civilian mission carrying humanitarian aid, including food and medical supplies, to a population that numerous international organisations, including the World Health Organization (WHO), have confirmed is already experiencing a man-made famine and widespread hunger as a direct consequence of Israel’s siege.
Israel's interception of the flotilla was, therefore, a direct act of obstructing, rather than facilitating, the passage of essential humanitarian aid to a desperate civilian population.
This constitutes a flagrant violation of the most fundamental humanitarian principles embedded in the law of armed conflict at sea.
Genocide and the machinery of blockade
The illegality becomes starker in light of findings by UN bodies.
In a report released in September 2025, the UN Independent International Commission of Inquiry on the Occupied Palestinian Territory, including East Jerusalem, and Israel, concluded that the State of Israel has committed the crime of genocide against the Palestinian people in Gaza.
The Commission, chaired by esteemed jurist Navi Pillay, found that Israel's actions fulfilled the criteria for four of the five prohibited acts listed under Article II of the 1948 Convention on the Prevention and Punishment of the Crime of Genocide.
The Commission's report is specific in identifying the acts that constitute genocide. Among these, it explicitly cites "imposing a total siege, including blocking humanitarian aid leading to starvation".
This directly corresponds to Article II(c) of the Genocide Convention, which defines as a genocidal act the "deliberately inflicting on the group conditions of life calculated to bring about its physical destruction in whole or in part".
The maritime blockade is the principal military and legal mechanism used to enforce this total siege.
It is the instrument that prevents ships from reaching Gaza, thereby controlling the flow of food, medicine, fuel, and all other goods essential for survival.
Consequently, the blockade is not merely a policy with harsh humanitarian consequences; it is legally identified as a core component of a genocidal act.
The Israeli Navy's mission was to stop a humanitarian convoy whose explicit purpose was to alleviate the very "conditions of life" that the UN Commission identified as genocidal.
The interception was therefore an affirmative act to protect and perpetuate an ongoing act of genocide.
The duty of the flag
The Law of the Sea imposes obligations on states whose vessels were attacked.
On the high seas, the law that governs a ship is the law of its flag state.
An attack by a warship on a civilian vessel is not merely an assault on individual passengers but an attack on the state whose flag the ship flies.
Under most domestic criminal laws and international law, acts of abduction and unlawful seizure of vessels on the high seas must be prosecuted.
Every flag state, therefore, has not only the right but also an obligation to investigate and, where appropriate, bring charges for crimes committed against its nationals and vessels.
In 2010, an assault on the Mavi Marmara killed nine civilians when Israeli soldiers stormed the vessel in international waters.
This time, Israel’s conduct has not been overtly lethal. The Sumud Flotilla was intercepted with force, but no massacre has yet been reported.
The change in tactics is telling. Israel has learned that it is losing the propaganda war.
Because the world is watching.
Millions across the globe follow every development of the flotilla in real time, and Israel knows it cannot afford the same images of brutality that followed the Mavi Marmara.
Yet a bloodless interception does not mean a lawful one. The underlying acts- the illegal blockade, the interception of ships on the high seas, the seizure of humanitarian cargo, and the abduction of crew- remain plainly illegal.
The only difference is that Israel now calculates that the appearance of restraint will help soften global outrage.
Why the law still matters
Ultimately, the Sumud Flotilla experience exposes once more the fragility of international law itself.
For decades, scholars and practitioners have debated whether international law really exists or is merely the reflection of power politics.
When a state like Israel, backed by the United States and shielded by European complicity, can openly violate the law of the sea, law of the occupation, and humanitarian law with total impunity, the sceptics’ argument gains force.
Israel continues to receive political cover, weapons, and legitimacy from powerful allies, even as its armed forces commit atrocities in plain sight.
Against such horror, one may ask: what weight do our words carry?
And yet, to abandon the law is to concede everything.
The law of the sea, like all international law, exists to protect the weak from the predations of the strong.
The principle that no state may extend its jurisdiction illegally beyond its territorial waters is one of the oldest and most fundamental norms in the global legal order.
If it is ignored here, the precedent ripples far beyond the Eastern Mediterranean.
The Sumud Flotilla matters not only for Gaza, but for the integrity of the international legal system.
If states can hijack ships on the high seas under the cover of an illegal “blockade,” no vessel anywhere is safe.
The task for the international community, and for every flag state whose citizens and vessels have been attacked, is to insist that this principle is enforced.
Whether those principles are enforced will tell us much about the kind of world we choose to live in: one governed by law, or one surrendered to impunity.
