California Revenue & Taxation Code
Cal. Rev. & Tax. Code § 9501
# (a)
Except as specified in subdivision (c), in addition to taxes imposed pursuant to Chapter 5 (commencing with Section 99500) of Part 11 of Division 10 of the Public Utilities Code, Part 2 (commencing with Section 7301), Part 3 (commencing with Section 8601), and Part 31 (commencing with Section 60001) of this division, on motor vehicle fuel, a tax may be imposed by a county on a countywide basis in accordance with this part.
# (b)
The tax shall be imposed in increments of one cent ($0.01) per gallon or, in the case of compressed natural gas, one cent ($0.01) per 100 cubic feet as measured at standard pressure and temperature.
# (c)
No tax shall be imposed under this part on fuel used in propelling an aircraft or a vessel.
Source: view the official text