It's a sign of the times that it takes 25 pages for a court to explain precisely why a dude who wears a baseball cap on his head -- or, for that matter, a yarmukule or dixie cup tied to a string -- doesn't get off on the grounds that he's wearing acceptable safety equipment under California's Helmet Law. Or, more accurately, why a dude with a baseball cap isn't entitled to merely a "fix-it" ticket that simply says "Eventually come to the police station with an acceptable helmet and we'll let you off."
Regardless, that's the law. Wear those absurd half-head helmets with the obviously fake DOT sticker and you may well just get a meaningless fix-it ticket. But flout the law even more and it's likely an actual ticket for you. That's basically 25 pages in two sentences.
P.S. -- "ThOus" on page 10 of the opinion should be "Thus". Let's run that spell-checker one last time.