Naturally European countries will be the most open; the point of the EU is to provide a federalized government and reduce divisions.
It's not unlike the federalized state created by the American colonies in the 18th century: no taxes on inter-state trade, no inter-state immigration restrictions, standard docs, etc.
It's not unlike the federalized state created by the American colonies in the 18th century: no taxes on inter-state trade, no inter-state immigration restrictions, standard docs, etc.