Despite the obvious hypocrisy how should that work? Get the chat apps a list of these people and their devices to exclude them from scanning?
Maybe the police could have a list and a posteriori don't investigate security police employees or politicians if they spread child sexual abuse material? Like an immunity. That is the only practical way to excempt them, unless they want to tell every api that they are Important Persons.
I guess such a list of all those people would be pretty valuable for criminal organizations.