You know, if you want to defend the legality of an action, you should probably not make your argument so ridiculous that it hurts your credibility.
Yet here we are.
Never mind the whole "it's not collective punishment" bit; I wouldn't expect a lawyer to be able to explain how cardamon and margarine are used in the production of bunkers, but whatever. How on EARTH can he pretend that the Gazans isn't an occupied, subject people when Israel has completely military control over the territory?
Gaza is not sovereign, not even close, and if it isn't sovereign then by definition it is occupied. And, yes, sovereignty matters; the United States is not permitted under international law to do whatever it feels like on sovereign territory to chase Al Qaeda; it either works with the sovereign states that actually control the territory (like Pakistan or Afghanistan) or goes into conflict with the sovereign states because they're helping Al Qaeda. Either way, it all comes down to who controls the territory: and in the case of Gaza, Israel does.
I was also really amused by the selective quotation of San Remo. If he knew about San Remo, and was drawing on San Remo (which may not even apply: that's a state-to-state conflict doctrine), San Remo makes it perfectly clear that you can't blockade goods in a way that causes disproportionate harm to the military benefits. Anybody and everybody can see that the harm is disproportionate. Under the law that he cited himself, the blockade is illegal.