An airport shall be marked as required by rule of the department with letters or symbol selected by the department to designate that the airport is not open to the general public. In selecting the letters or symbol, the department shall be guided by letters or symbols currently in use by the Federal Aviation Administration for similar or comparable purposes.
Source:
Section 21650.1, https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=PUC§ionNum=21650.1..