So, the part of Gaza that Israel's gonna attack first, the north, is the opposite side from the side that Egypt controls access to, the south. Israel is informing Gazan civilians to flee towards the south. Egypt can hand over food and water at any time. Second, siege warfare is very arguably permissible under international law. https://lieber.westpoint.edu/siege-law/ - The key is, the besieging side should not try to target civilians, which Israel is complying with by instructing Gazan civilians to flee south. It is unjust to hold Israel to a higher standard than the standards to which other nations are held. What Israel is doing complies with the letter and intent of international law.