May I introduce you to the "rolling coal" morons?

No need. I've seen them.

In the States, for example: Every state I've looked at has laws that make it illegal to roll coal.

And at least in my own state (Ohio), it's a primary offense. A person can be pulled over and ticketed for this even if they're doing everything else by the book. It's super easy to spot.

It seems that it persists not because of a lack of laws, but because of a lack of enforcement.

do you really think there’s no way to prevent or penalize that behavior without preventing the user from owning and operating their own engine?

also, what scale of harm do you think exists from those people?

do you really believe that control of one’s own engine should be removed from all vehicle owners if a few people misuse it?

do you understand that vehicle manufacturers use their proprietary systems that control the vehicle to exploit customers?