Nathan,
That could be the situation, that the police were illegally taping the event.
Then again, I'm not sure Will would be in a position to know why the police were videotaping the event, or that the police in fact were the ones who made the tape.
We know they ultimately were priveledged to view or have access to it. There are too many variables without definative answers to the questions to accuse law enforcement of any wrongdoing.
It was a public event, there would be no expectation of privacy at such an event, and unless there were some restriction from the organizers or owners of the property stating no video filming on the premises, there would be no crime committed unless sound was used on the tape [ which may or may not kick the wire tapping laws into effect ].
It is an assumption and speculation on his part and others to believe otherwise until these questions have been answered.
Some states have two party consent, others only one party to be legal and I'm not sure about this particular venue.
I'm unclear at this point if there were a registration of any kind at that time, but I may have missed something.
Brownie