I watched this video, but skipped through some sections where I thought there was no discernable audio. Did the audio ever reveal the actual California statute that was being invoked? I heard that question asked, but I didn't hear that it was answered. The original officer said, "You can't have anything protrude more than 2mm off your helmet." and "You can't have anything on your helmet that compromises integrity."
I was curious, so I thought I'd do a little internet research. (OK, I guess I may have too much time on my hands!)
I found the California helmet laws, but couldn't find anything in their statutes regarding helmet protrusions or attachments. It may be there, I just couldn't find it. The officer mentioned the "2mm protrusion". This sounds like a reference to Federal Law regarding helmets where the Fed statute mentions a 5mm specification. The officer may have simply remembered the dimension incorrectly. I found these Federal statutes:
https://www.govregs.com/regulations/title49_chapterV_part571_subpartB_section571.218
S5.5 Projections. A helmet shall not have any rigid projections inside its shell. Rigid projections outside any helmet's shell shall be limited to those required for operation of essential accessories, and shall not protrude more than 0.20 inch (5 mm).
The heading for this Part 571 has a statement on the Applicability for the statutes therein:
https://www.govregs.com/regulations/title49_chapterV_part571_subpartA_section571.7
§ 571.7 - Applicability.
(a) General. Except as provided in paragraphs (c) and (d) of this section, each standard set forth in subpart B of this part applies according to its terms to all motor vehicles or items of motor vehicle equipment the manufacture of which is completed on or after the effective date of the standard.
If this is the source of the California violation, I think it could be argued - as it has successfully in other jurisdictions - that this 5mm limit applies to the helmet manufacturer, but not the helmet user. I suppose one would have to go to California court to get the issue clarified.
I hope cameras remain legal as I think they provide a valuable resource like dash cams. Also, though I admit a helmet-camera may present some additional risk to the rider (and perhaps others when they fly off), we make these risk/reward decisions every time we climb on our bikes.
I also agree that this rider was a total ass.