In terms of contemporary International Law - or at least in terms of how it is currently weaponized against Israel - it is necessary to question it's very beginning following WW2:
Could the Allies have fought as they did, yet while applying the humanitarian standards that are now being imposed on Israel?
Would these standards have allowed the Allies to win the war at all?
The answer is No. And not only because neither the Japanese Kamikaze nor the German camp guards were receiving humanitarian aid from the US, the UK or the USSR. One could also think, for example, of the nuclear bombs in the Japanese case and of ethnic cleansing in the German case (nowadays that would be considered "genocide") . The Allies didn't even comply with the much thinner humanitarian law of their own time. Because of these and many other reasons, the warfare of the allies against their (i.e. our) enemies was, in fact, in total juxtaposition to the rules Israel is expected to comply with now, having been attacked so viciously.
This is not just unjust or unfair, but of crucial importance: Had the allies fought in compliance with "International Law", they would have lost. As simple as that. That is to say:
We would have lost.