The Fourth Geneva Convention, adopted in 1949 sets out rules that protect civilians in a time of War.
Section III deals with the issue of territories occupied by a foreign army during war, setting out provisions that:
Article 47: Guarantee the rights of the occupied population
Article 49: Prohibition transfers of the population – this article states specifically : “The Occupying Power shall not deport or transfer parts of its own civilian population into the territory it occupies.” It also prohibits the “individual or mass forcible transfers, as well as deportations of protected persons from occupied territory”.
Amnesty International has laid out some ways that Israel is violating International Law in its occupation of Palestinian territories.