Just because your car can hold it's lane and not run in to traffic doesn't lessen your responsibilities on the road. If I was that officer I would write the driver a ticket for driving without due care and attention.
I have a car with adaptive cruise control, that doesn't mean I don't have to be ready to use the brakes; it just means I don't have to use them myself as often. Most of the times the cruise control uses my brakes is when a car changes in to my lane in front of me.
If I had a Tesla I would probably use the autopilot a lot, I would still pay attention to the road though.