What do dotted line borders mean?

[Darth Tribble]

I just finished a game last night and I had a war with Russia. Before the war, their borders were solid, but after I dropped some nukes and captured a couple of their cities, they ended up having dotted line borders.

What does it mean when the borders are dotted lines?

 

[Canadian Bluebeer]

Dotted lines normally means open borders, or early on, they haven't discovered how to block borders.
Crossing solid lines means war.

They have given you open borders in a peace treaty.

 

[Scaramanga]

Dotted lines mean the borders are porous.