Once Palestine becomes a state, it can join the ICC and launch criminal complaints against important Israelis. For example, Lieberman is also a settler, thus guilty of a war crime. An indictment by the ICC will make him persona non grata around the world, and will force Israel to get him out of the Foreign Ministry. It is likely that his party will then leave the coalition and Netanyahu will either call new elections or bring in Kadima. This is just an example of an indirect influence Palestine will have. Of course, the ICC threat will affect other settlement actions, so the Israeli political considerations will be changed profoundly.
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from the article: Abbas predicts 'very difficult' time for Palestinians after UN bid