I do not like the fact that the AI will cross into my territory without a non-aggression pact. It means that to maintain a border, I have to manually scan all of my territory, click on the enemy unit and tell them to leave. It creates a lot of unnecessary extra clicks for a human player. I think the default setting should be, "I don't want any other factions in my territory. If you want through, declare war or ask for a non-aggression pact."
