CA vehicle code section 26708(a)(1). Basically you cant add anything to thie windows according to this. Even the stuff about sun screen stuff is clear. hope it helps!
26708. (a) (1) A person shall not drive any motor vehicle with any
object or material placed, displayed, installed, affixed, or applied
upon the windshield or side or rear windows.
(2) A person shall not drive any motor vehicle with any object or
material placed, displayed, installed, affixed, or applied in or upon
the vehicle that obstructs or reduces the driver's clear view
through the windshield or side windows.
(3) This subdivision applies to a person driving a motor vehicle
with the driver's clear vision through the windshield, or side or
rear windows, obstructed by snow or ice.
(b) This section does not apply to any of the following:
(1) Rearview mirrors.
(2) Adjustable nontransparent sunvisors that are mounted forward
of the side windows and are not attached to the glass.
(3) Signs, stickers, or other materials that are displayed in a
7-inch square in the lower corner of the windshield farthest removed
from the driver, signs, stickers, or other materials that are
displayed in a 7-inch square in the lower corner of the rear window
farthest removed from the driver, or signs, stickers, or other
materials that are displayed in a 5-inch square in the lower corner
of the windshield nearest the driver.
(4) Side windows that are to the rear of the driver.
(5) Direction, destination, or termini signs upon a passenger
common carrier motor vehicle or a schoolbus, if those signs do not
interfere with the driver's clear view of approaching traffic.
(6) Rear window wiper motor.
(7) Rear trunk lid handle or hinges.
(8) The rear window or windows, if the motor vehicle is equipped
with outside mirrors on both the left- and right-hand sides of the
vehicle that are so located as to reflect to the driver a view of the
highway through each mirror for a distance of at least 200 feet to
the rear of the vehicle.
(9) A clear, transparent lens affixed to the side window opposite
the driver on a vehicle greater than 80 inches in width and that
occupies an area not exceeding 50 square inches of the lowest corner
toward the rear of that window and that provides the driver with a
wide-angle view through the lens.
(10) Sun screening devices meeting the requirements of Section
26708.2 installed on the side windows on either side of the vehicle's
front seat, if the driver or a passenger in the front seat has in
his or her possession a letter or other document signed by a licensed
physician and surgeon certifying that the person must be shaded from
the sun due to a medical condition, or has in his or her possession
a letter or other document signed by a licensed optometrist
certifying that the person must be shaded from the sun due to a
visual condition. The devices authorized by this paragraph shall not
be used during darkness.
(11) An electronic communication device affixed to the center
uppermost portion of the interior of a windshield within an area that
is not greater than 5 inches square, if the device provides either
of the following:
(A) The capability for enforcement facilities of the Department of
the California Highway Patrol to communicate with a vehicle equipped
with the device.
(B) The capability for electronic toll and traffic management on
public or private roads or facilities.
(12) A portable Global Positioning System (GPS), which may be
mounted in a 7-inch square in the lower corner of the windshield
farthest removed from the driver or in a 5-inch square in the lower
corner of the windshield nearest to the driver, if the system is used
only for door-to-door navigation while the motor vehicle is being
operated and outside of an airbag deployment zone.
(c) Notwithstanding subdivision (a), transparent material may be
installed, affixed, or applied to the topmost portion of the
windshield if the following conditions apply:
(1) The bottom edge of the material is at least 29 inches above
the undepressed driver's seat when measured from a point 5 inches in
front of the bottom of the backrest with the driver's seat in its
rearmost and lowermost position with the vehicle on a level surface.
(2) The material is not red or amber in color.
(3) There is no opaque lettering on the material and any other
lettering does not affect primary colors or distort vision through
the windshield.
(4) The material does not reflect sunlight or headlight glare into
the eyes of occupants of oncoming or following vehicles to any
greater extent than the windshield without the material.
(d) Notwithstanding subdivision (a), clear, colorless, and
transparent material may be installed, affixed, or applied to the
front side windows, located to the immediate left and right of the
front seat if the following conditions are met:
(1) The material has a minimum visible light transmittance of 88
percent.
(2) The window glazing with the material applied meets all
requirements of Federal Motor Vehicle Safety Standard No. 205 (49
C.F.R. 571.205), including the specified minimum light transmittance
of 70 percent and the abrasion resistance of AS-14 glazing, as
specified in that federal standard.
(3) The material is designed and manufactured to enhance the
ability of the existing window glass to block the sun's harmful
ultraviolet A rays.
(4) The driver has in his or her possession, or within the
vehicle, a certificate signed by the installing company certifying
that the windows with the material installed meet the requirements of
this subdivision and identifies the installing company and the
material's manufacturer by full name and street address, or, if the
material was installed by the vehicle owner, a certificate signed by
the material's manufacturer certifying that the windows with the
material installed according to manufacturer's instructions meets the
requirements of this subdivision and identifies the material's
manufacturer by full name and street address.
(5) If the material described in this subdivision tears or
bubbles, or is otherwise worn to prohibit clear vision, it shall be
removed or replaced.
