First of all, "In cases not covered by this Protocol or by other international agreements, civilians and combatants remain under the protection and authority of

First of all, "In cases not covered by this Protocol or by other international agreements, civilians and combatants remain under the protection and authority of the principles of international law derived from established custom, from the principles of humanity and from the dictates of public conscience." (Article 1, second paragraph, Additional Protocol I.) Second, both Israel and Palestine have signed the main conventions. Israel with reservations, and have not signed AP I and II. Palestine have signed all of them, unconditionally. Since both are signatories, they are both bound by the conventions even if the other party breaks them.