"""The term chemical weapon is applied to any toxic chemical or its precursor that can cause death, injury, temporary incapacitation or sensory irritation through its chemical action. Munitions or other delivery devices designed to deliver chemical weapons, whether filled or unfilled, are also considered weapons themselves.""

Seems pretty plain that this would preclude the sale of precursors to suspect regimes.

So selling to Iraq or Syria would seem to be illegal under the agreement, for any signatory.

If the US or UK have sold to those countries any precursor, they are in breach.

QED

Don T.