Klaus,
"but it's not easy to proof that something dosn't exist anymore"
Thats the whole point! 30,000 Chemical/Bio Capable shells do not simply vanish into thin air when their disposed of or destroyed. Understanding what happens to these weapons when their disposed of and destroyed is the key to understanding why there is no such thing as "Something not existing".
Iraq had 10,000 Liters of Anthrax and 30,000 Chemical/Bio capable shells when UN inspectors were forced to leave in 1998. That is a fact that not even the Iraqi's disputed. If Iraq destroyed all 30,000 Chemical/Bio Capable shells between 1998 and 2002 as they claim, they have the responsibility to show the evidence of that destruction. 30,000 shells is an unbelievable amount of metal.
10,000 Liters of Anthrax if disposed of would leave behind plenty of trace elements or residue that investigators could pick and examine.
Disposal of this material is not like a saturday morning cartoon where someone waves a magic wand and "poof", it disappears.
More importantly, any disposal of WMD by Iraq after inspections started was required to be observed and verified. Failure of this in any way shape is a material breach of Iraq's obligations under the Ceacefire Agreement and grounds for military action.
The Weapons Inspectors were withdrawn because that phase of the UN operation was a failure and required the cooperation of the Iraqi government to work. Military enforcement of the resolutions is a new phase and the only alternative the international community had to ensure Saddam was disarmed. In this new military phase, it is the military's responsibility to ensure that Iraq is disarmed. The time for peaceful inspections and peaceful disarmament of Iraq has long since passed.