"Iraq's chemical weapons have some special staus because it is the only country since World War One to actually use them"

Not actually true. The United Kingdom used them in what was then called Mesopotamia, in the 1920s (now it's called Iraq) - and that was against the Kurds as well.

And of course the United States used enormous quantities of Agent Orange in Vietnam - and people are still dying from it, in a second and third generation, mostly in Vietnam, but also in the USA.

If the weapons inspectors are free agents, not in the pocket of some government, I'd be happy to accept their judgement on this, if they ever get allowed to go in. (And I have the US in mind as the most likely people to stop them going in, I'm afraid, even more than Saddam.)