"British Home Secretary Theresa May announced Monday that a police inspectorate will examine possible police corruption.
She told lawmakers that at moments like this 'it is natural to ask whom polices the police' . . ."
Natural--if you don't know the Queen's English. Otherwise, you would ask who polices the police. It is not the pronoun that is the object of the verb, but the whole indirect question. The pronoun is the subject of this indirect question.
Nieces and nephews that read this blog: pay attention and Uncle John will reward you with candy.
By the way, it is nice to see "police" used as an adjective, verb and a noun in just two lines.