Alright, let's treat them like cars then :-)
Scooter riders should be licensed. They need to take an exam, including a road and written test.
Need to pay city parking fees. Respect parking zones. Only park in designated areas. Areas change in a complicated pattern depending on weather, time of day, day of the week or scooter type and color.
If they violate that they get confiscated and need to pay a fee to get it back.
They also need to be insured in case they hit a pedestrian.
Riders who speed get mailed speeding tickets from speed cameras
Getting caught inebriated on a scooter on a sidewalk should be a serious offense, with points taken off and a corresponding insurance fee hike. Possibly court appearance as well.