Town/City (Kansas) forcing owner to prove a registered and tagged vehicle be driven and prove it runs. Is this legal or can you fight it?

Why has this become an issue? Is it parked on a public street without being moved for a long time? Most towns of any size have laws against storing a nonoperational vehicle on a public road, or limit how long an operating vehicle can be parked. You would have to check the local laws and regulations to know, but generally a law enforcement agency is not going to require you to do something that is not a legal requirement

@laughter_every_day forcing aka being served papers. It can only be some town ordnance for having multiple vehicles parked on your property. Papers served requires police officer to ride along to prove the vehicle works.

Parked in back yard/lot of private property.

You can fight anything. I once had a bunch of tickets for not having a city sticker in one town that I worked in, when it had a sticker for the town that I lived in. I talked to the city attorney and she agreed to give me a free city sticker for that town, so the police would not be confused and ticket me for parking there at night.

Call the City Attorney and ask what they want, why they want it, and what you have to do.

Cities don't like it when their citizens junk up the place. Sure it's legal. Sure you can fight it. Hope you lose. Fix it and drive it or dump it. Life is too short for people to have to put up with eyesores e.g. as rotting vehicles.

This likely comes down to where you've been parking it.

If this was on the street or in your front yard, they can demand this.

Depends. What does the town Ordinance say?

Yes, legal.