The land-owner/manager can always regulate who lands there, but they never own the airspace and every significant airspace issue has always gone to the FAA for jurisdiction. For something unintentional like an emergency landing, I would think the court would still decide in the favor of the defendant, since even if they were regulating landing there would have to be the intentionality for it, vs. emergency/act of god/etc. I don't think that flies in court, like you break down on the road and it happens to just be my property you have to pull off on and so I get to keep your car? There are often issues that get complicated in retrieving it, but I think ultimately they are usually decided in favor of the defendant getting their stuff back.

That said, there are two sides to every story and there could be more going on than originally described, like intentional landings, water-skiing with the airplane, etc.