Suffice it to say that:
the UN resolutions condemning the blockade render it illegal under international law.
No resolution stating that its illegal that I know of. Only states the easing of restriction of humanitarian channels.
Human rights council, sure, but they're one of the worst departments that have a selective OCD only to Israel. Read the bit about the head commending actions against the Tamil Tigers.
even if this were not the case, for a blockade to be legal under the San Remo memorandum of armed conflict at sea, both sides in the conflict must be states subject to the laws of war (and in this case Gaza is not).
State of armed conflict, which is applicable even to a non-state entity like Hamas. Trying to apply laws of war to asymetrical war practices of groups like Hamas as been a hot debate topic.
even if this were not the case, there is a carve out for humanitarian aid
Humanitarian corridors are open, have been since the blockade was put into place, and will continue to do so. This circumvents the San Remo clauses regarding the humanitarian corridors.
even if this were not the case, any use of force must be proportionate to the threat posed to the state using it and 6 humanitarian ships pose no threat to Israel.
Only 1 ship posed any sort of 'resistence', the rest were quietly and orderly detained using the same methods that was initially applied to the ship that had the mob of 'peace activists' on it. This answers proportionality.
Neutral ships, according to the San Remo clauses already posted, can be detained and their goods confiscated (which were diverted to Gaza yesterday). This answers the question that a neutral ship does not have to pose a threat if it threatens to enter the evasion zone of a naval blockade.
even if this were not the case, any use of force must also be proportionate to the threat posed to the soldiers using it and a few kitchen knives and wooden sticks are NOT a proportionate threat to justify 9+ gunshot deaths.
Death ratio has nothing to do with the proportionality clause. You continue to make the use of deadly weaponry, from metal pipe, knives (didn't even see any of the kitchen type), pistols and improvised explosive devices against the IDF as innocuous.
even if this were not the case, imprisoning civilians and taking them to Israel is illegal.
No it isn't. Detaining those aboard the neutral vessel are released once they are brought to port. There's no imprisoning.
Given all of these points, claiming that IDF acted lawfully is fundamentally impossible.
These points don't stand up to scrutiny.