Your views on the definition of, and legality of a blockade, may be interesting to some, but they are not relevant to the Israeli blockade of Gaza. Historically, international law has determined a blockade's only legitimate objective is to weaken military forces of the enemy. In this context, Gaza is not a fortified city, fort nor castle. The Israeli blockade does not target armed forces but an entire population. That's a violation of international law. Throughout the history of siege warfare, there were never a UN and international laws protecting innocent civilians. There are now. Israel is in violation of article 33 of the 4th Geneva Convention. Article 33 forbids collective punishment of a civilian population. Violation of the article is considered a war crime.
from the article: Rights groups: World has betrayed the citizens of Gaza