The US gov't did this during Prohibition. Google Jake Leg for an interesting tale of Jamaican Ginger Extract, poisoning, and permanent paralysis.
[edit] Wrong. The gov't began testing the extract for ginger solids to ensure it was unpalatable, so those selling the extract replaced the ginger with a chemical to pass the gov't test. That chemical was toxic and caused permanent paralysis. The gov't was not responsible, but one could easily point at this national tragedy as another failure of any sort of prohibition. Vote Ron Paul 2012. (see what I did there?)