The police don't have to, but the casino sure as hell would have if the NFL asked for it. Why would the casino be obligated to honor a request from the NFL? Because they're a casino and it's the NFL asking. A possibly even easier route to the tape would have just been to ask Ray Rice himself. Odds are pretty high his attorney would have a copy as it was evidence in a potential criminal case. Rice wouldn't have been in a position where he could say no.