The Stoics believe in the theory of cosmopolitanism.
Basically, this is that we are all part of one big family, where borders don’t exist.
In a cosmopolitan society there is no need for passports.
No immigration control.
No borders or checkpoints.
We are all citizens of one blue planet floating around in space.
There would be no need for a global government because we are doing thing for the good of humanity and the planet.
How much different would life and society be if everyone started doing things for the good of the planet rather than some fleeting short term gain?
(There is a worthwhile discussion on it in this post by Kai Whiting and Leonidas Konstantakos)