Thats a good point.
California allows frames as long as they do not cover/obscure any information, including the issuing state (so the OP’s cover, which obscures the word “ohio” at the top would be deemed illegal in CA). license plate covers, on the other hand, are illegal in CA, even if they are clear.
From Section 5201 of the Vehicle Code, as amended by Section 15 of Chapter 90 of the Statutes of 2016:
(2) The installation of a license plate security cover is not a violation of this subdivision if the device does not obstruct or impair the recognition of the license plate information, including, but not limited to, the issuing state, license plate number, and registration tabs, and the cover is limited to the area directly over the top of the registration tabs. No portion of a license plate security cover shall rest over the license plate number.
( c ) A casing, shield, frame, border, product, or other device that obstructs or impairs the reading or recognition of a license plate by an electronic device operated by state or local law enforcement, an electronic device operated in connection with a toll road, high-occupancy toll lane, toll bridge, or other toll facility, or a remote emission sensing device, as specified in Sections 44081 and 44081.6 of the Health and Safety Code, shall not be installed on, or affixed to, a vehicle.