If we make it a server rule it'll be broken regularly.
This is because we can have the server console messages telling people to read the rules, here on the forums, cover the screen and be neon orange and people will still either not bother or not see them!
Plus the only ways to police it would be either having the admins trawl through the playerfiles every so often or form a server police group.
Neither of which is gonna happen.
Besides, regardless of what price tag you stick onto a BS, people are still gonna trade and trade until they can get one.
The only viable way to stop players using capships is to remove them.