California
Vehicle Code – VC § 5201.1
VC § 5201.1. Sale of product or device that obscures reading or recognition of a license plate prohibited; Operation of vehicle; Avoidance of visual or electronic capture of license plate or characters; Violation; Punishment
(a) A person shall not sell a product or device that obscures, or is intended to obscure, the reading or recognition of a license plate by visual means, or by an electronic device as prohibited by subdivision (c) of Section 5201 .
(b) A person shall not operate a vehicle with a product or device that violates subdivision (a).
(c) A person shall not erase the reflective coating of, paint over the reflective coating of, or alter a license plate to avoid visual or electronic capture of the license plate or its characters by state or local law enforcement.
(d) A conviction for a violation of this section is punishable by a fine of two hundred fifty dollars ($250) per item sold or per violation.