JERUSALEM — Israeli naval forces, far from the country’s shores, intercepted and seized a Gaza-bound ship carrying international activists, including Greta Thunberg, in an early morning raid Monday. The operation sparked accusations that Israel’s actions, apparently in the high seas, were a breach of international law.

The activists say their journey was meant to protest Israel’s ongoing war in Gaza and the humanitarian crisis there. The ship was carrying aid destined for people in Gaza, including baby formula and food. The activists, including Thunberg, were detained and were headed to Israel for likely deportation.

It’s not the first time Israel has halted ships carrying aid bound for the Palestinian territory. A raid in 2010 descended into violence between activists and Israeli commandos, leaving eight Turks and one Turkish-American killed. Most of the other operations against Gaza-bound boats have ended uneventfully, with ships diverted and activists detained.

Israel says the latest ship planned to violate its blockade on Gaza and says it acted in accordance with international law.

Can Israel storm a ship in the high seas? Here is a look at the legal debate.

Intercepted Far Off the Coast of Gaza

The Freedom Flotilla Coalition, which organized the latest ship, says the Madleen was intercepted in international waters about 124 miles off the coast of Gaza, a claim that could not be independently verified. Israeli authorities have not disclosed the location where the ship was halted.

Robbie Sabel, an international law expert and former legal adviser to the Israeli Foreign Ministry, said the U.N. Convention on the Law of the Sea stipulates that a state only has jurisdiction up to 12 nautical miles from its shores.

In general, states don’t have the right to seize ships in international waters, but there are exceptions, including during armed conflict, Sabel added.

He said that even before the latest war, Israel was in an armed conflict with Hamas, allowing it to intercept ships it suspected were violating its longstanding blockade of Gaza, which Egypt also enforced. Rights groups have long criticized the blockade as unlawful collective punishment against Palestinians.

Sabel cited a U.N. report on the 2010 raid that ended in activist fatalities, which stated that “attempts to breach a lawfully imposed naval blockade place the vessel and those on board at risk.” The debate over the legality of Israel’s blockade remains unresolved among legal experts.

The U.N. report urged states to be cautious in the use of force against civilian vessels and called on humanitarian missions to deliver aid through regular channels. It said a country maintaining a naval blockade “must abide by their obligations with respect to the provision of humanitarian assistance.”

A Debate over Israel’s Right to Act

Yuval Shany, an expert on international law at Hebrew University in Jerusalem, said that so long as Israel’s blockade of Gaza is “militarily justified” — meant to keep out weapons — and the ship intended to break it, Israel can intercept the vessel after prior warning.

Whether the blockade is militarily justified is also up for debate.

Suhad Bishara, head of the legal department at Adalah, a legal rights group in Israel representing the activists, said Israel was not justified in acting against a ship in international waters that posed no military threat.

“In principle, Israel cannot extend an arm into international waters and carry out whatever action against a ship there,” she said.

Israeli Foreign Ministry spokesperson Oren Marmorstein said that “everything that was done was done in accordance with international law,” referring to the ship takeover.

Gaza and Israel’s Obligations Under International Law

Rights groups say the legal questions are complicated by Gaza’s unique status.

The United Nations and much of the international community view Gaza as Israeli-occupied territory, along with east Jerusalem and the West Bank, all of which Israel captured in the 1967 Mideast war. The Palestinians want the three territories to form their future state.

Israel argues that it withdrew from Gaza in 2005, when it pulled out its soldiers and settlers, even though it maintained control over Gaza’s coastline, airspace and most of its land border. Hamas, which does not accept Israel’s existence, seized power in Gaza two years later.

Amnesty International says Israel has an obligation as the occupying power to make sure that Palestinians in Gaza have enough access to humanitarian supplies, something Amnesty says Israel was preventing by not allowing the Madleen through.

Amnesty and other groups see the seizure of the Madleen as part of a campaign by Israel throughout the war to limit or entirely deny aid into Gaza.

Israel says it has allowed enough aid to enter Gaza to sustain the population and accuses Hamas of siphoning it off, while U.N. agencies and aid groups deny there has been any systematic diversion.

Israel’s aid policy during the war has driven the territory toward famine, experts say, and Prime Minister Benjamin Netanyahu is accused by the International Criminal Court of using starvation as a method of warfare by restricting humanitarian aid into Gaza, charges he has rejected.

“By forcibly intercepting and blocking the Madleen, which was carrying humanitarian aid and a crew of solidarity activists, Israel has once again flouted its legal obligations towards civilians in the occupied Gaza Strip,” Amnesty International’s secretary general, Agnès Callamard, said in a statement.

The group called for the immediate and unconditional release of the activists, who it said were on a humanitarian mission.