Not my perception,nor of that of experts in international law. I guess we will need to agree to differ.Perfectly justifiable under the Nuremburg and Geneva Conventions.
Below is a link to an interview with Geoffrey Robertson QC, judge and expert in International law on a review of the UK's involvement on the Iraq war.
http://www.youtube.com/watch?v=xxX9OZlVUjI
In brief: the international consensus is that the invasion of Iraq was indeed illegal under international law. However,international law is not the same as national law;it has no police force. That means the war criminals involved in the Iraq war will never be prosecuted. I invite you to watch the video (10 minutes)