Earlier quoted context omitted.
In some countries it's done so and poisoning is banned. E.g. Finland and Poland got an exemption from the EU to do this because so many people died from the poisonings.
Where can I read more about this? What poison were they using?
https://en.wikipedia.org/wiki/Denatonium is used to make it unpalatable. Fun fact: the same chemical is also coated onto Nintendo Switch cartridges to discourage children from putting them in their mouths.