What makes possible to move through foreign territories while you do not have military access?

I noticed sometimes I can move through neutral territories without asking for military access.

What makes this possible ?

Solution 1:

a) exile - This is symbolized by the black flag next to oyur army. Exile occurs mainly, when a war ends and your army is hostile territory. You will be able to move through it, but cannot fight and must move to one of your provinces.

b) Automatic military access. From the wiki: Countries automatically gain military access to countries that grant military access to someone they are at war or allied with.

I.e. if you are in a war, you will have military access to allied and enemy countries. Furthermore, any military access treaty of an ally is expanded to you and vice versa.

This means, if you are Spain and allied with Austria. You enter a war together with Austria. If Austria has military access from France, you will also have access to travel through France.