There are a ton of supercars in the Middle East. When they're breaking the law, you need a cop car that can actually chase them down. That's why you need an Aventador cop car.
Pictures of this car have been making the rounds on the world wide interconnected internets but there's not much information about the vehicle out there.
I tend to doubt it's actually a real Dubai cop car, but instead is probably a promotional vehicle or something that an absurdly rich owner modified in order to gain a little favor with the local cops.
Still looks pretty cool.
Update: Dubai has confirmed that this is actually one of their cop cars! Furthermore, they are now going to add a Ferrari to the fleet.