Questions about outlawed adventurers

[Buffalkill]

If an adventurer enters a realm from which he's been banned, is he arrested automatically, or does it require someone to notice and decide to arrest him?

[Anaris]

If an adventurer enters a realm from which he's been banned, is he arrested automatically, or does it require someone to notice and decide to arrest him?

No one's ever arrested automatically. You always have at least a chance of sneaking by.

[Buffalkill]

Does it require a player action or is it a game mechanic?

[OFaolain]

Does it require a player action or is it a game mechanic?

You can be arrested by militia; I've had an adventurer get captured that way before (his realm was at war with the realm he had wandered into).  So I would presume that player units also have a passive chance to capture you, but I could be mistaken.

[Chenier]

Probably only if your new realm is at war with the old realm.

[Indirik]

I'm fairly certain that it takes a war declaration before anyone is arrested via automated mechanics.