All discussions regarding law/use case etc are irrelevant.
Just explain WHY one should not be able to turn the AP back if you think this is not a bug.
And as a use case, just imagine a straight stretch of a road, you are traveling on AP on some set speed, and there is a car driving next to you, so you just want to move ahead a bit so the car on the right does not stuck on your blind spot all the times.
So you hit go pedal for a sec or two, and as the car is so fast it would easily do 90mph for a moment.... and than boom, no more AP until the end of your trip.
Does this sound reasonable to you?