In my opinion, there is a legal basis for challenging such a violation. For instance, there is no way for the ticketing officer to tell whether the vehicle is even capable of operation, unlike a vehicle which is parked on a public highway. The real question is whether the ticket, which is a non-moving violation involving a fine only is worth fighting about. Hiring an attorney to fight a fine only ticket that won't in any way affect your driving record sounds like a bad deal to me. If you fear this will happen frequently, you only have two options: 1) be prepared to fight it every time, or 2) buy a city sticker and keep it up to date.