First, a link explaining more of illegal wars.
http://www.huffingtonpost.com/...tional-law_b_1324303.html

Second, DH, I am not defending Iran. I have said here that they are irrational and any war of aggression by Iran against Israel would be as illegal a preemptive FS. I believe in peace, not unilateral force. Brute force rarely works and just pushes the problem into the future with additional fodder for anger. The threat from Iran is not certain and could be mostly election rhetoric. That statement also fits Israel.

Third, Iraq did not have intercontinental missiles and the flight path of such cannot be intercepted by current anti-missile technology.

Fourth, the UN does not impinge on national sovereignty. However, it is a framework agreed to by sovereign nations to govern international relations. The UN is mostly toothless and cannot enforce resolutions, but as a signatories, the US, Iran, and Israel, should seek the approval of the international community prior to unilateral force.