Yes, Israel is a signatory, I don't know about Palestinian, I doubt they would since only sovereign states sign the agreement. In any event, not signing the convention does not alleviate the responsibility to behave according to the convention's tenets. These are humanitarian rules that must be obeyed by all humanity.
The fact of the matter is that Israel has prosecuted some of its soldiers when they were found violating their oath (Israeli soldiers swear an allegiance like all soldiers in the world, but that allegiance also includes a strict requirement that soldiers keep their arms "holy" (it is difficult to translate, in this case it means the arms will not be stained with innocent blood), and a number of Israeli soldiers which either due to "bad character", the pressure of battle, or even innocent battle errors have unnecessarily harmed civilians, are serving heavy jail sentences.
Zeev