I am also curious in the source and rationale. As I am unaware of any prohibition.
I'd be interested as to whether or not this was actually a "Lawyer" or a paralegal. Not to say anything bad about paralegals but I expect a LOT more from one than the other.
Also as far as I'm aware there is nothing out there preventing you from recording police executing their job in public. They wear name tags and/or badge numbers for a reason. So long as you're doing it in a way that doesn't make his/her job harder to do you're good.