[alter_eco123]

You know, in practice, even your passport has always been a "permission to leave".

It's also a "permission to enter" some other country. But without it, you won't be flying anywhere.

Then you've got visas, which are "permissions to exist" in a certain geographical area (within a certain time-frame).

We've all had a default assumption that we can get a new passport any time, but it's actually never been guaranteed.

[gambiting]

Not long ago even European countries had double borders - you had to go through one checkpoint of your own country, that would verify that you can leave(you are not a wanted criminal for example), and then another checkpoint of the country you wanted to enter, to check if you have the right to enter it. The area between the two was the no-mans-land. This arrangement still exists between some South American and African countries, you have to go through two separate checkpoints.

[alter_eco123]

> Not long ago even European countries had double borders

Our current situation might be marginally better than "double borders", but you're probably aware we're headed in a police statey direction all over the world.