A former human colony decides that it's done with deep space, and wants to come home to earth.
Say, a couple thousand people.
Earth replies "No thank you"
These earthward bound former colonists respond "I believe we are human and that is our homeworld too and we have every moral right available to resettle in the lands our ancestors helped build up just as much as yours did."
Who is verbally repelling this "invasion"?
The Human Government of Earth or the Federation seat in Paris?
Is there still a United Earth Government?
Do you really think that aliens, roll a dice, the president is most likely an alien, but even then he or she is only a mouth piece for a hundred and 50 member worlds of which earth doesn't have a voice since the federation Council speaks for earth who has a representative Counsellor on site who can't speak for earth if Earth has no voice... As I was saying, do you really think that aliens have a right to tell humans beings that they are not welcome on Earth?
If the United Earth Government still exists, what does it do if the Federation seat already does everything? ...And why would the Federation Counsellors agree to Govern Earth or speak for earth when it sets a precedence that could see their own world turned into an annex just like Earth?
The Non interference policy that may or may not be the prime directive says that the Federation stays out of internal matters.
What if two member worlds go to war?
Does the Federation pick a side or wash their hands of both?
How can two member worlds go to war if everything is decided on earth and no member world has it's own voice?
The Novels claim that Mars is a member world separate and unique of Earth.
What if Mars and Earth decided to go to war?
What Earthlings do within Earthspace sounds like Earthly problems to me... However as the mildy retarded ugly sister of the founding members I can also seeing humanity symbolically leasing or selling Earth to the Federation to act as the government of the Federation to assure it's seat at the table... But from the original 5, the youngest Federation wouldn't need a whole world to govern the itself, maybe just a non aligned space station in neutral space?
Do member worlds retain any sovereign rights? Their own unique governments, or are they all slaves whose soil is occupied by Federation troops dictating right from wrong?
That seems unlikely.
All this, Vulcan on Vulcan, ditto.