The flotilla is on the High Seas and not in Israel’s 12 mile territorial sea. Israel has no jurisdiction.
An attack by a state military warship on a vessel on the High Seas is an attack on the flag state of the vessel attacked.
The possession of vessels and the abduction of crews at sea can be pursued as a crime in domestic jurisdictions and is not just a crime under international law.
Craig Murray, former head of the maritime section at the UK’s Foreign and Commonwealth Office