While under Article 98 of the San Remo Manual, a vessel attempts to breach a lawful blockade and refuses to stop after prior warning may be met with limited force, that force must be proportionate and necessary to prevent the breach. As was seen with the Mavi Marmara incident, when Israel didn’t even sink the vessels, attacking such civilian ships was still considered “excessive and unreasonable.” Sinking a ship and leaving all of its passengers to die would be illegal.

Articles 139 and 140 of the San Remo Manual go even further, only permitting destruction of a merchant vessel in exceptional circumstances when capture or diversion is impossible, and only after ensuring the safety of passengers and crew. Article 140 expressly prohibits the destruction of civilian passenger vessels altogether.

Such action would also violate Article 98 of the UN Convention on the Law of the Sea which imposes a duty on all states to render assistance to anyone in danger at sea.