Corner crossing is illegal if you don't have permission to be on private land. Don't like it, buy the land you want to cross or negotiate a trespass fee.
The low altitude airspace being part of the property is just the way it works.
Then it should be no problem for you to point out the specific statute and language in statute saying corner crossing is illegal.
Good luck with that.
It's Wyoming 6-3-303. It's impossible to cross the corner without illegally entering the property of one (or both) of the other corners. If proper notice has been given (and the picture of the signs shows that it has been), it's trespassing which is why he was arrested and charged and will be convicted if he doesn't plea out.
Read the statute, no mention of airspace in title 6-3-303...point out where air space is mentioned or implied.
