Let's take the model for just war as presented in the Catechism of the Catholic Church, to which Blair will have committed when he converted to Rome on leaving office. It couldn't be clearer. "Once all peace efforts have failed" (so Blair's war already doesn't qualify) "legitimate defence by military force" may be used if the following criteria apply: "The damage inflicted by the aggressor on the nation or community of nations must be lasting, grave and certain" (there were no WMDs); "all other means of putting an end to it must have been shown to be impractical or ineffective" (chief weapons inspector Hans Blix wanted more time); "there must be a serious prospect of success" (no planning was made for success); "the use of arms must not produce evils and disorders graver than the evil to be eliminated". On that last point, just look at post-invasion Iraq, not to mention Afghanistan, or for that matter July 7, 2005 in London.