I've had a couple of cases where I had peace with a neighbor, but no open borders treat. In one case, my influence was so great I had covered one of his systems completely in my influence, but I still couldn't move to the planet. I think influence should determine what systems I can go to, not the system owner.

He still owns the system, not you. Therefore you cant travel there since you have no open borders. Think of it in a real life situation. Just because say 1 country has 90% or even 100% of its borders surrounded by another, doesnt mean that other country can move through it if they dont have open borders. Just because the borders are very small, doesnt mean they are not still there.



Now for this game, say, by sheer chance if its even possible, you completely overwhelm their solar system with your influence, they still OWN the solar system, meaning its theirs, meaning thats their border, therefore you cannot enter.