I experimented an interesting multiplayer situation :

- Roving Clans cannot declare war.

- Morgawr can black spot (it allow free attack and conquering of city).

So, if a Morgawr black spot a Roving clans and conquering him a city, the Roving Clans cannot take back their own city, because it would need to declare war. So unless you defend without any less, you cannot do anything.

I don't complain because I don't see what could be done, and it's a very marginal problem. But it's very unlogical. ^^