After reading through the rules, there is a lot of mention of a Government controlling a planet by population through building facilities like High Rises.
What I am NOT understanding, is personal planet control.
Let me pose a question of sorts for what I THINK I understand... If an individual who is part of a faction, were to go out into deep space away from faction controlled space, find themselves a nice small moon somewhere and build a city on it, they could not be called the definitive "Owner" of the planet through the building of facilities? They would have to put a slab owned by them down on EVERY surface of said moon?
Is this the only way that someone could prevent a faction from coming along and building some facilities to take control of the planet/moon?
A person cannot control a planet like a government. The only way for someone to control a planet on their own is via the following options:
1) Have a city on every square that won't decay, to prevent any more cities from being built (obviously you may not want to do this and it can look ugly)
2) Have enough cities in strategic locations to build a shield grid to prevent unauthorized access. Shields cover a 3x3 area of the planet's surface, centered on the city where the shield is located (so the city, and 1 square in every direction)
3) Have a government that likes you hold enough of the flats to maintain control for you.
Otherwise, the planet will appear as uncontrolled and anyone can build a city on an empty terrain square.