Just for once I have to agree with Oleg here. I really don't think
that direct movement restriction are such a good idea.
For one thing when a player moves he is up to twenty or thirty days
away from the entity declaring the attitude. How should such a remote
entity directly prevent a player from moving in any direction he
wants ? What happens if the attitude changes while the unit is moving
on the road ? If there is nobody in a controlled region, _who_ stops
the movement ?
In addition, I think that this prevents perfectly legitimate movement
eg. by units with high stealth who should not be either stopped or be
forced to fight. They should be able to penetrate enemy provinces.
The problem is not really foreigners coming into a province against
the will of the ruler. The problem is unwanted foreigners coming into
a province, making use of the market, entertaining, killing a few
people and then moving on before the month is over without the ruler
being able to do anything.
The good and realistic solution to this province is to allow
auto-attacks. In the combination with the default attack mode that
easily allows you to automatically attack and capture any unwanted
foreigners immediately when they come into your land. Then you can
dispose of them as you want, including just dropping them off again
in the province they came from.
If you absolutely want to warn people, announce in the OT or put up
posts in all neighboring provinces. But don't add yet another not
really necessary unrealistic artifact to Olympia.