Sapo I appreciate that you’re fighting your ignorance here. I think a lot of people resist fighting their ignorance about anything controversial at the SDMB because they don’t have a clear and well-formed position themselves and know they’ll get torn to bits in GD.
You’re still confusing your legal and moral arguments. You don’t believe that Israel’s attacks on Gaza cross a moral line. A lot of people disagree with you. Those people may cite international law to show that there is a moral consensus or to add legal weight to their argument or to point out Israel’s hypocrisy but I don’t think many people think that Israel’s actions are immoral simply because they break international law. If international law didn’t exist you’d have the same people arguing that the Gazans don’t deserve what they’re getting for the same - moral - reasons.
A lot of people, BTW, agree with you, including the US government, but they don’t argue that proportionality is itself a flawed standard, just that killing hundreds of innocent civilians is not disproportional against an existential threat to Israel when the enemy combatants are deliberately using civilians to shield themselves. Everyone, including you, agree that some things would be disproportionate, such as genocide or nuclear war - even if we all agreed that was what it would take for Israel to be permanently safe.
Your legal claim is that we don’t need international law to tell us that some things are beyond the pale. But while you might not, the world does. Genocide was long considered a purely internal affair between a country and its minorities. (See Armenian genocide.) The idea that genocide is always and everywhere wrong and that other nations have a right and a responsibility to intervene is an idea that was promulgated through international law.
And then what about things like nuclear weapons? We dropped a nuclear weapon (two of them) on a country, when we arguably didn’t have to. You may think it is clearly a wrong thing to do, but people still argue today about how we ended WWII. But now we have countries like Britain and France and Israel and India and Pakistan and Russia who all have nuclear weapons. We’re on more-or-less friendly relations with all of them, but we don’t want to trust the limitation of nuclear war to our current diplomatic friendships. So we get India and Pakistan to agree not to use nuclear weapons in a conventional war. And agree to the same thing, and we get all the other nuclear countries to go along with it, partly to pressure India and Pakistan (of course these weren’t the countries we were worried about when this happened, but it makes the point), and partly to make sure that if one of them breaks the treaty they don’t have any allies because all those countries agree that nuclear weapons are wrong in a conventional conflict, and partly because we really don’t want Britain or France or Israel using nuclear weapons either. And maybe we have to give up something, like using biological weapons, in order to get those countries to go along. Of course if we can’t use biological weapons, we don’t want anyone else to either, and the country making the demand wants everyone else to agree as well, so that we won’t have any allies if we break the treaty. And pretty soon everyone has agreed to certain rules of warfare - not based on some abstract moral principle and not because the UN came and made us, but because everyone benefits, even if some things get banned that no rational actor would do anyway and some things get banned that would end wars more quickly. And that gives moral weight to people who argue against things like genocide and chemical weapons and torture, but it also puts up practical barriers to using those things because it galvanizes international opinion and isolates countries diplomatically who don’t follow the rules.
So from a legal perspective, what is it about this system that you think should be changed and what should replace it?