Is it permissible to work with the police in a European country to guide them to drug dealers, knowing that most of them are Arabs and Muslims by name, and do not adhere to religious teachings such as prayer and drinking alcohol?

It is permissible to work in apprehending criminals and preventing their evil, as long as it does not lead to oppressing people. The fact that the perpetrators of crimes are Muslims does not matter, because corruption must be prevented from whatever source it originates. One must also be aware of the dangers of residing in lands of disbelief.