Guy Gardener wrote:
unless the entire solar system is reclassified as Earth and the other planets and dwarf planets and smaller, are legally regarded as countries from Earth or even cities from Earth.
I think that this would basically be it.
Unless they were in some fashion separated from Earth officially, they would be a part of "Earth." Other star systems that are linked to Earth (colonies, etc.) would also be a part of "Earth."
Mr. Laser Beam wrote:
^ Mars is a Federation member world in its own right, and is independent from Earth.
That would be an official separation. As long as there wasn't a adversarial relationship ("how dare you leave us") things should be fine. Now if Mars as a sovereign state choose to be independent okay, but if they joined another interstellar organization besides the Federation (which would be their right) things could get messy.
It is an alliance and you certainly can leave. It's like EU. You think rest of the EU countries are going to send their armies to invade Portugal if it chooses to leave the EU?
The United Kingdom might be a better example than Portugal, since as a population they are currently discussing separation from the EU.
I don't think the Federation would have a "the door locks behind you" rule.