In the UK we only allow pedal assist ebikes up to 15mph. If they meet the requirements, then it counts as a bicycle and follows other rules. If not, like a higher speed or it provides power without pedaling, its a motorbike or vehicle so has to meet those requirements (licence plate, annual mot check, mandatory insurance etc) which by definition they would not be able to so are illegal. Its pretty easy to spot them. You see a few, a lot food delivery people have them but they are running the risk of police tickets or impounding every time they go out.

Would be interesting to see what other countries are doing too