I really hope that if anyone that is not in your tribe or friendly with your tribe enters your tribes land you can kill them with no penalty.
Having everyone wandering all over your lands and not being able to stop them without becoming evil won't be fun. I plan on treating tribe lands like I do my actual property, you come on it without my permission and you're gonna get your ass handed to you on a silver platter.
A good reason for this would be to stop spying. Since players can design their own cities, other tribes might want to spy and find the weakest point, or see what resources are where so they can raid and take them.
So having it be a safe zone in prelude only for the owning tribe would be a better idea in my opinion, it might not matter so much now but it will when the protection is gone and they already know all your weaknesses.
Also is a slightly unrelated matter, we have to ward off visitors so how about......heads on pikes?.......too much?....lil bit?