I am speaking about national sovereignty over land, not ownership rights. Of course, private owners of parcels of land will retain them, except paying property

I am speaking about national sovereignty over land, not ownership rights. Of course, private owners of parcels of land will retain them, except paying property taxes to a different state and being bound by different laws (probably getting residence permits in a new country, too, to enable access to their property). This is annexation, not foreclosure-like sale.