Kevin, I'm not an attorney, but I wouldn't think it was 'illegal' since they had space available. Now, if you were stuck without a space, I would be livid.
Their reaction to the situation is what makes this tolerable or not. I can't imagine somebody suing or calling the police over a $45 spot (not sure of what you paid). By the time you tried to sue, it would cost way more than the frustration and trouble (if it were illegal).
If the park was full and they had no place for you, giving you a refund would obviously be the right thing to do but still very frustrating.
I'm sure the laws vary by state so maybe a lawyer will chime in to give you right answer.
I've seen RV parks do crazy things that just don't make sense. My brother and his wife were traveling in their motorhome following us. We stopped near Dearborn, MI, at a RV that used to be a KOA but has another name is now run down. This visit was actually our second not realizing we had stayed before until we pulled up. It's the closest RV park to the Ford museum. What a dump. I will not make the mistake of staying there again.
Anyway, we wanted to be next to each other in the pull-through section. The clerk (older lady...meaning older than me) said no, we can't put you together. So, there was a spot in-between us that no body used until the last night of our three night stay. The other 4 or 5 pull through's were never used. It just didn't make sense.
Sometimes, people are just stupid. The bad thing about the park that we stayed in is that there fire rings are at the front wheel on the passenger side. Makes no sense whatsoever. I had to move our coach closer on the driver's side when leaving so that I could reach the dump outlet. When leaving, I almost fell into my neighbors fire pit hole with my driver's side tire. Thank goodness I saw it before I turned too sharp.
I wondered if I could have sued over that if I fell into that hole, it was covered with grass it was hard to see.
Mark