system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:If SpaceX founds a Moon colony,whose law applies? Can they simply declare Elon Musk Republic?
gpt
National sovereignty is defined by having the force to defend your borders & getting recognition from other countries.  We have some laws about space but it's all very abstract since nobody's meaningfully had the capability of colonizing there.

A huge practical difficulty would be that terrestrial governments who disapproved of the colony would have control over terrestrial launches of resupply missions.  If the base wasn't self-sustaining, it would be at the mercy of terrestrial governments to allow those launches.

If you were self-sustaining, you'd be pretty much independent until a planetary government thought it was worth the immense expenses involved in sending a bunch of space marines up to subjugate you.  At that point, you'd have to fight something akin to the American Revolution - a war with a superior but vastly distant power.