I know it's an actual legal principle, asshole, and don't call me ignorant. But it's not like the state requires you to have a license to longboard, whereby you would have to go to a class and learn all the laws. And there aren't any legal hoops you're required to jump through in order to obtain a longboard, so the city/state has SOME obligation to inform people of the most basic laws that govern such a benign activity. These days "no skateboarding" signs are almost as common as "no parking" signs, so the ABSENCE of any such warning would almost denote its legality. At the very least, the dude deserves a warning before he gets stuck with a ticket that big.
Obviously, the guy doesn't have a great leg to stand on if he wants to challenge this, but I stand behind my arguments, even though they probably wouldn't work.
And btw, I'm not pulling this shit out of my ass, I've interned at a law firm, taken a handful of law classes in undergrad, and plan to go to law school next year and eventually pass the bar in CO. I know I'm not a lawyer or anything yet, but I know more than you might think about what flies and what doesn't.
This guy's biggest problem is that he ISN'T a lawyer, so it'd be hard for him to get a judge to take him seriously, and if he hired one he'd obviously pay more than $110 for it.
"Just ahead, over the rolling wheatfields all golden beneath the distant snows of Estes, I'd be seeing old Denver at last. I pictured myself in a Denver bar that night, with all the gang, and in their eyes I would be strange and ragged like the Prophet who has walked across the land to bring the dark Word, and the only Word I had was 'Wow!'"