I'm new here but here is California law right from there site
There are two definitions of motorized bicycle (moped). A motorized bicycle is:
A two- or three-wheeled device, capableofnomorethan30mphon level ground, and equipped with:
Fully operative pedals for human propulsion.
A motor producing less than two gross brake horsepower and an automatic transmission.
An electric motor, with or without pedals for human propulsion. (CVC §406[a])
A vehicle with pedals and an electric motor (not more than 1,000 watts) which cannot be driven at speeds of more than 20 mph on level ground even if assisted by human power. (CVC §406[b])
If you operate a motorized bicycle which meets the definition of CVC §406(b), you:
Must be 16 years of age or older.
Must wear a properly fitted and fastened bicycle helmet.
Are exempt from the motor vehicle financial responsibility, driver license, and moped plate requirements. (CVC §12804.9)
You may ride a moped in a bicycle laneatareasonablespeed.Becareful of bicyclists using the lane.