Whose exactly? A country is just a name for a place on a map with lines squiggled around it. No property rights are broken crossing them. A country isn't the same as private property. People have a god given right to travel the realm freely.
Discussion
It belongs to the one willing to defend it, like all property. That is usually whoever is already in possession of it.
Property rights trump freedom of movement.
Funny how many animal species understand & yet so many humans seem not to... 🤣