its not but in the instance of Thutben Darge Ling (Rinpoche's 1st gompa back in America) it was either exterminate the rats or the authorities will close down the gompa. They had not much of a choice.
If faced with such a problem, peoples should firs try to displace garbage cans, raise the level of area cleanliness and they would naturally leave. Only when such measures fail, you could try wit extermination. It seems to me that "killing the pests" is more often done for convenience rather than necessity. In which case is understandable.
i heard that they had to do it immediately and it was too late for the cleanliness thing. the authorities gave them 24 hours or so to take action or face eviction.
i am not too sure of the full story but perhaps wai meng could get more info of it. this is all of the info i could get