The only substantial legal question is whether the arrest of the flotilla was legal. On one hand these were international waters, on the other hand the flotilla intentions were publicly stated. I wonder how come in the international legal community, the answer to this simple question hasn't received a unanimous clear cut answer. Law is not an exact science, but the incident doesn't seem to be so legally complicated. My understanding is that the arm siege on Gaza is internationally legal, whence breaking it illegal. Since the flotilla intentions were to break this siege, its intentions were illegal and the interception is consequently legal. The notion of "non-proportional force" is a non-issue due to the armed resistance of the flotilla, as exemplified by wounding Israeli soldiers. The humanitarian issue is also not here because, the flotilla had the opportunity to unload its cargo in Egypt or Israel - to be transferred to Gaza. This my understanding but I am not a Lawyer.
Netanyahu orders more demolitions of terrorists' homes in attempt to crack down on terror (Haaretz)
from the article: UN rights body names team to probe Gaza flotilla raid