California Code, Revenue and Taxation Code - RTC § 17041.5

Notwithstanding any statute, ordinance, regulation, rule or decision to the contrary, no city, county, city and county, governmental subdivision, district, public and quasi-public corporation, municipal corporation, whether incorporated or not or whether chartered or not, shall levy or collect or cause to be levied or collected any tax upon the income, or any part thereof, of any person, resident or nonresident.

This section shall not be construed so as to prohibit the levy or collection of any otherwise authorized license tax upon a business measured by or according to gross receipts.