Via The Telegraph:
Tony Blair sidelined the Cabinet over the decision to invade Iraq because he feared ministers would leak sensitive material to the press, the head of the civil service has said.
For the moment, this speaks for itself and to the nature of the Blair government, but I’m looking forward to the eventual report of the Iraq Inquiry.
In the meantime, you may wish to read the brief treaty which is the Kellogg-Briand Pact of 1928. It provided for the renunciation of war as an instrument of national policy. Obviously, it failed, but Great Britain was a signatory and I understand it is still in force.