Joining the Police In non Muslim countries

Referring the question to Dr. Monzer Kahf,  Scholar in Islamic Economics & Financial Expert, he said,

It is of course permissible, unless you are not allowed to pray or you are forced to do some non-permitted actions such as spying on any other person, Muslims or non-Muslims. To the best of my knowledge, the UK police force does not require a Muslim to do any such things and rather it has Muslims in it too.