Israel has released nearly all of the 175 activists detained after its navy intercepted the Global Sumud Flotilla in international waters off Crete, but has retained two of its organisers for questioning in what governments across Europe are calling an unlawful seizure. The Spanish-Palestinian activist Saif Abukeshek and the Brazilian Thiago Ávila were taken ashore in Ashkelon on Saturday, while their fellow passengers disembarked on the Greek island. Viewed from Madrid, the detention of a Spanish citizen aboard an Italian-flagged vessel in waters far from any Israeli jurisdiction is a clear breach of international law.

Spain’s foreign minister, José Manuel Albares, described the arrest as illegal and beyond Israel’s authority, while Prime Minister Pedro Sánchez characterised it as a kidnapping. In Rome, the legal team representing the flotilla has filed a criminal complaint with the Rome prosecutor’s office, arguing that the seizure amounted to aggravated abduction, and has also lodged an urgent appeal with the European Court of Human Rights against the Italian state for failing to protect its flagged vessel. Analysts in London note that the incident reignites a long-running tension between the right of peaceful protest at sea and Israel’s naval blockade of Gaza, which it defends as a security necessity.

The flotilla, which set sail from Barcelona in mid-April carrying humanitarian supplies, was dismissed by Israel’s foreign ministry as a public-relations stunt. Yet organisers insist the mission will resume, claiming they have already mobilised new volunteers from across Europe. The two detained men face interrogation over alleged links to Hamas—a charge their supporters vehemently deny.

For Brussels and other European capitals, the affair poses an uncomfortable question: how to respond when a close security partner intercepts their citizens in waters that, while international, fall within the European Union’s maritime backyard. With legal proceedings now under way in multiple jurisdictions and diplomatic protests escalating, the episode looks set to test the limits of European solidarity and the reach of Israeli deterrence far beyond the shores of Gaza.