Whenever visibility limitations pose a significant safety hazard, as determined by a member of the California Highway Patrol, that member may restrict or prohibit the use of any highway by any vehicle subject to regulation by the Department of the California Highway Patrol pursuant to Section 34500.
Source:
Section 2812.5, https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=VEH§ionNum=2812.5..