Evelyn Gordon explains why Israelis are so skeptical of the UN Jenin "fact-finding" mission: Since the basic facts about Jenin are now pretty much universally agreed upon, and since none of the commission members have a background appropriate for evaluating wartime actions in the light of international law, it appears that the real purpose of the mission is to prepare the ground for war crimes charges that the UN has already decided that it wants.

One sticky point, I think, is that international law relates to whether or not a military action has a "valid military objective". Israelis (and I think most sensible people) consider eliminating terrorist bases to be a valid military objective, but it's quite likely that the UN won't think so - especially since the UN ( the UN HRC actually) has passed a resolution vaguely approving Palestinian attacks on Israeli civilians.