From Consumer Wiki
Consumers may check with city or county for ordinances for regulation of taxicab fares.
Meters which monitor mileage for calculations of fees for taxicabs or buses should exhibit a sticker emblem showing inspection by the California Department of Food and Agriculture, Division of Measurement Standards.
Regulations are enforced by inspectors in individual counties throughout the state. Random selected inspections are the usual method for accomplishing compliance with state regulations. Problems can be reported to the consumer's local County Weights and Measures office.