"No use using the excuse - "they were old/forgotten about" - they still existed, against UNSCRs."
Except that these are reports of weapons that MIGHT have contained banned agents with no confirmation of what the follow up investigations actually found.
Except that we were 'sold' the idea of invading Iraq on the basis that Saddam had an active chem/WMD programme and represented a credible and robust and present NBC threat (you'll remember the 45 minute nonsense) and NOT merely that he had screwed up the disposal of long-retired and forgotten weapons.
A possible, minor, technical breach was not what people had in mind when the WMD threat was used to justify the war.
And there have been plenty of legal, moral wars, from GW1 (Iraq had invaded Kuwait), and the Falklands, to Korea and the two big ones.