Unless the answer is the Bush 43 Administration, I don't see where this question is relevant. That's the same argument the shakedown artists are using to try to get *cough* "reparations."
The most obvious case occured by Klinton and Reno at Waco. I'm sure there are others too.
My point is this: what's the difference between Sadaam Hussein and Janet Reno?
If the threat of a foreign power using chemical weapons is just cause for war, should not the deed of actually using them against US citizens be a crime?
Until this adminstration goes after the criminals the used chemical weapons at Waco, their argument against Iraq (with respect to chemical weapons) holds no credibility.