That's not the biggest problem: All drivers have to obey hand signals from policemen and other people who are authorized to direct traffic. Which means your car has to know what police officers and state troopers and highway patrol and mounties look like where you happen to be located right now, and not be confused by some dude dressed up as one. Oh, and it has to understand the hand signals as well.
I don't think it's reasonable to expect either car or human to determine the distinction between "person dressed as cop" and "sworn police officer acting in accordance with his duties".
Probably shouldn't anyway. It's not unusual for civilians at the site of some unexpected hazard to warn traffic.
Good luck little car.