I doubt that we would need to make human driving illegal. More likely automated cars become so popular and cheap that a generation grows up without learning how

I doubt that we would need to make human driving illegal. More likely automated cars become so popular and cheap that a generation grows up without learning how to drive manually and outside of a subset of enthusiasts human driven cars simply start to disappear from the market. We already have driving assistance systems like ABS and computers which will automatically apply brakes which can reduce the risk of accidents but we don't mandate that all vehicles on the road use them.