It deals with the definition and treatment of protected persons in Occupied Territory. It doesn't say a word about the acquisition of title/sovereignty. Further if you claim that title to land may no longer be acquired by conquest in a DEFENSIVE war, you will have to show that that is the international norm. However, you will not be able to show that. There were at least 20 incidents where states acquired title by war between 1948 and 1975 (not all of them defensive either.) Only about 1/4 of them were internationally condemned. The rest were accepted. Israel was the only case where the UN demanded that the victorious party withdraw. Law which is not applied in the same normative fashion in all cases is, to put it bluntly, not legal. No body thinks you can pass a law making speeding illegal, and then enforce it only for people who own red cars. In the same way, you can't have an international law that says acquisition of territory in a defensive war is illegal, and enforce it only with respect to Israel.
Abbas: West Bank arson is a 'crime against humanity', vows to petition ICC (Haaretz)