The laws of occupation, incorporated in the Hague Convention (1907) and in the Fourth Geneva Convention (1949), impose general responsibility on the occupying state (Israel) for the safety and welfare of civilians living in the occupied territory (the Gazans).
Israel must protect the wounded, sick, children under age fifteen, and pregnant women, enable the free passage of medicines and essential foodstuffs, enable medical teams to provide assistance, and refrain from imposing collective punishment during an armed conflict. Given that Israel contends that an armed conflict exists between it and the Palestinian organizations fighting against it, which has continued even after the disengagement, such provisions from international humanitarian law apply.
Source: B'Tselem - The Israeli Information Center for Human Rights in the Occupied Territorieshttp://www.btselem.org/gaza_strip/israels_obligations