Don't cite the 4th Geneva Convention as it does not apply - Gaza is not occupied. In order for there to be an occupation, the occupying power must have effective control. This means it has replaced the territory’s government's authority with its own. Hamas, however, reigns supreme in Gaza. An occupation cannot exist when a territory’s government has full control over its territory. A blockade is not an occupation. If you wish to cite customary international law, then I expect to see you cite the two requirements for it to be applicable to Israel: State Practice and Opinio Juris.
from the article: Israel releases papers detailing formula of Gaza blockade