Ref. No. 1050/41-209
In the name of Allah the most Gracious the most Merciful
The answer to your question is as follows:
It is duty of every citizen to abide by the rules of the country as strictly as possible. So they should avoid slaughtering cows whilst other options are available. When other animals can be slaughtered in Qurbani, slaughtering cow and consequently poisoning the country environment is against Islamic norms and etiquettes. Nevertheless, if a person did so he has fulfilled the duty of slaughtering and discharged his responsibility.
And Allah knows best
Darul Uloom Waqf Deoband