[lazide]

Regarding you first point - fences around your land are perfectly fine (barring some other law, like an environmental protection law, zoning, whatever).

But it is illegal to block access to federal public lands. So you’d need to have some way through. Doesn’t have to be on the corner, it could be an easement or whatever somewhere else, but access can’t be blocked.

They intentionally did it to block people though, and try to defacto claim the public land as theirs - which is illegal.