Israeli authorities said the activists on board, including Greta Thunberg, were safe and being transferred to Israel.

The Global Sumud Flotilla, composed of nearly 50 boats and 500 activists, was carrying a symbolic amount of humanitarian aid to Gaza.

What international maritime law says

The U.N. Convention on the Law of the Sea stipulates that a state only has jurisdiction up to 12 nautical miles (19 kilometres) from its shores.

In general, states don’t have the right to seize ships in international waters, though armed conflict is an exception to this.

Yuval Shany, who specializes in international law at Hebrew University in Jerusalem, explained that if Israel’s blockade of Gaza is “militarily justified” — aimed at preventing weapons from entering — and the ship’s intention is to breach the blockade, Israel is permitted to intercept the vessel after issuing a prior warning.

Whether the blockade is militarily justified and the legality of the blockade is a point of contention.

But the flotilla argues they are a civilian, unarmed group and that the passage of humanitarian aid is guaranteed in international law.

Omer Shatz, an Israeli expert in international law who lectures at Sciences Po University in Paris and co-presented a previous flotilla case to the Israeli supreme court, informed The Associated Press that even if the contentious siege of Gaza is regarded as lawful, “international law creates a humanitarian passage from the open sea to Gaza — both in international and national waters off Gaza,” he stated.

“If the fundamental needs of the population are not met by the occupying power, there exists a right to deliver humanitarian aid, though under specific conditions,” Shatz highlighted.

For instance, Israel reserves the right to board and inspect the vessels carrying aid to verify their cargo, similar to the procedures it follows with aid trucks that cross into Gaza by land.