Once Palestine joins the ICC, the court's jurisdiction will provide coverage against human rights violations in the Palestinian territories, regardless of whether the source of such violations is Israel or the PA itself. In other words, this will establish a foundation for the prevalence of the rule of law in the Palestinian territories.
"Israel will gradually lift roadblocks, checkpoints and military closures throughout the West Bank. We are extending the security and governance responsibilities of the Palestinian Authority to all of Area B and much of Area C. We will work with the Palestinian Authority to do so in a systematic manner...."
Every single day Israel continues its occupation and colonial settlement activities, it is acting unilaterally. The idea that it will take another unilateral move does not scare Palestinians who have little more to lose through their newfound, albeit tiny, act independent of their Israeli occupiers.