The Israeli raid of the so-called "freedom flotilla" trying to run the blockade was a PR disaster for Israel, but some of the accusations by the pro-Gaza activists are just way out of line. The activists have claimed everything from high-seas piracy to unprovoked attack and so on. When they use hyperbole like that, and press cover them, but does not reveal the truth, the media has succumbed to the "spin".
The truth is the flotilla had been warned multiple times they are sailing into an internationally announced blockade of a terrorist organization, Hamas. They were warned before they sailed, after they sailed, AND once again before they entered the blockade area. In fact, the Israelis offered to escort them to Israeli port where the goods can be transshipped to Gaza... after inspection.
The international law on blockade zones is actually pretty simple: if the ship knowingly sails into a blockade zone and/or suspected of carrying contraband, does NOT stop upon being challenged, and/or actively resists being stopped, the ship can be attacked. Frankly, the ship can be SUNK, legally. The Israeli commandos actually exercised considerably restraint as they beat back the the 60-100 metal bar wielding thugs without causing even MORE casualties, other than 9 of the thugs killed.
For what laws are in effect, read this: