Although the wisdom of Israel's actions in stopping the Gaza flotilla is open to question, the legality of its actions is not. What Israel did was entirely consistent with both international and domestic law. In order to understand why Israel acted within its rights, the complex events at sea must be deconstructed.
First, there is the Israeli blockade of Gaza, which included a naval blockade. Recall that when Israel ended its occupation of Gaza, it did not impose a blockade. Indeed it left behind agricultural facilities in the hope that the newly liberated Gaza Strip would become a peaceful and productive area. Instead Hamas seized control over Gaza and engaged in acts of warfare against Israel. These acts of warfare featured anti-personnel rockets, nearly 10,000 of them, directed at Israeli civilians. This was not only an act of warfare, it was a war crime. Israel responded to the rockets by declaring a blockade, the purpose of which was to assure that no rockets, or other material that could be used for making war against Israeli civilians, was permitted into Gaza. Israel allowed humanitarian aid through its checkpoints. Egypt as well participated in the blockade. There was never a humanitarian crisis in Gaza, merely a shortage of certain goods that would end if the rocket attacks ended.
The legality of blockades as a response to acts of war is not subject to serious doubt. When the United States blockaded Cuba during the missile crisis, the State Department issued an opinion declaring the blockade to be lawful. This, despite the fact that Cuba had not engaged in any act of belligerency against the United States. Other nations have similarly enforced naval blockades to assure their own security.
The second issue is whether it is lawful to enforce a legal blockade in international waters. Again, law and practice are clear. If there is no doubt that the offending ships have made a firm determination to break the blockade, then the blockade may be enforced before the offending ships cross the line into domestic waters. Again the United States and other western countries have frequently boarded ships at high sea in order to assure their security.
Third, were those on board the flotilla innocent non-combatants or did they lose that status once they agreed to engage in the military act of breaking the blockade? Let there be no mistake about the purpose of this flotilla. It was decidedly not to provide humanitarian aid to the residents of Gaza, but rather the break the entirely lawful Israeli military blockade. The proof lies in the fact that both Israel and Egypt offered to have all the food, medicine and other humanitarian goods sent to Gaza, if the boats agreed to land in an Israeli or Egyptian port. That humanitarian offer was soundly rejected by the leaders of the flotilla who publicly announced:
"This mission is not about delivering humanitarian supplies, it's about breaking Israel's siege on 1.5 million Palestinians." (AFP May 27, 2010.)
The act of breaking a military siege is itself a military act, and those knowingly participating in such military action put in doubt their status as non-combatants.
It is a close question whether "civilians" who agree too participate in the breaking of a military blockade have become combatants. They are certainly something different than pure, innocent civilians, and perhaps they are also somewhat different from pure armed combatants. They fit uncomfortably onto the continuum of civilianality that has come to characterize asymmetrical warfare.
Finally, we come to the issue of the right of self defense engaged in by Israeli soldiers who were attacked by activists on the boat. There can be little doubt that the moment any person on the boat picked up a weapon and began to attack Israeli soldiers boarding the vessel, they lost their status as innocent civilians. Even if that were not the case, under ordinary civilian rules of self defense, every Israeli soldier had the right to protect himself and his colleagues from attack by knife and pipe wielding assailants. Less there be any doubt that Israeli soldiers were under attack, simply view the accompanying video and watch, as so-called peaceful "activists" repeatedly pummel Israeli soldiers with metal rods (see http://www.youtube.com/user/idfnadesk). Every individual has the right to repel such attacks by the use of lethal force, especially when the soldiers were so outnumbered on the deck of the ship. Recall that Israel's rules of engagement required its soldiers to fire only paintballs unless their lives were in danger. Would any country in the world deny its soldiers the right of self defense under comparable circumstances?
Notwithstanding the legality of Israel's actions, the international community has once again ganged up on Israel. In doing so, Israel's critics have failed to pinpoint precisely what Israel did that allegedly violates international law. Some have wrongly focused on the blockade itself. Others have erroneously pointed to the location of the boarding in international waters. Most have simply pointed to the deaths of so-called peace activists, though these deaths appear to be the result of lawful acts of self-defense. None of these factors alone warrant condemnation, but the end result surely deserves scrutiny by Israeli policy makers. There can be little doubt that the mission was a failure, as judged by its results. It is important, however, to distinguish between faulty policies on the one hand, and alleged violations of international law on the other hand. Only the latter would warrant international intervention, and the case has simply not been made that Israel violated international law.