Enforcement? We'll See...

Helmet use on motorized scooters (AB 2989, Flora): Bicycle helmets are no longer required for riders of motorized scooters who are age 18 or older. Motorized scooters may operate within a Class IV bikeway as well as a Class II bikeway and on highways with speed limits up to 25 miles per hour. Local jurisdictions may pass ordinances to allow motorized scooters on highways with speed limits up to 35 miles per hour. It is still illegal to operate a motorized scooter on a sidewalk.

Source: https://patch.com/california/santamonica/s/gl4p4/traffic-safety-laws-coming-to-ca-in-2019