Recently, the engine in my car went bad and I cancelled my insurance to save up money to deal with the problem. The car looks fine, it just has no plates and was sitting in my driveway. Without any warning, while I was out, park management towed my car. It was on a Friday, so I had to wait until Monday to contact anyone about this. My roommate, who owns the trailer I rent a room in, said this happened to someone else. AFTER the car was towed, management told her since her car had to tags, she should have covered it up. I'm sure what they are doing is illegal. Not only towing people's cars from their private driveways, but then forcing them to pay fees to get them back. Is what they're doing legal? I don't think it is.
It is legal, unless it is a violation of the rental agreement. Generally, a property owner can have a vehicle towed from their property, although there may be a requirement in the state to post a towing notice. If the lease agreement says that cars must always be street-legal, that is the end of the discussion. If the agreement says that cars without tags or plates can be stored in a person's spot, towing it would be a violation of the agreement. If the agreement doesn't say anything, then the property owner's rights would be the default deciding factor. Since your roommate seeks to override the park owner's ordinary control over the surrounding spaces, there needs to be an explicit provision for that in the lease.