First - such legal quibbles as arguments are used only because your side has run out of other, more fundamental objections, MacLeod:
Concerning the moral side, your position is falimentary;
Even with regards to the legal side (as per current law, that is), as long as you don't come with highly improbable speculation such as your last post, you have no argument (simply put, the federation has AT LEAST* the legal right to invoke eminent domain; it didn't only in order for the baku NOT to appear as the elitist jerks who could care less about anyone else they are).
The baku did not settle unclaimed space.
Because when this space was claimed by the klingons, they would have searched their new property and evicted these few hundreds of luddites with extreme prejudice, especially considering what a clement/valuable M class world these luddites were on.
The baku's possession of that planet - during klingon reign, at least - was not visible, but hidden - if it was visible, the klingons would never have allowed it.
And hidden possession will not lead to adverse possession no matter how much time passes.
As for the federation - even if it knew about the baku and let them stay on the planet: possession by the allowance of the owner will never lead to adverse possession, no matter how much time passes.
*Eminent domain is invoked to get land from its rightful owner
, for reasons of public utility/interest, after compensation - and it doesn't matter whether this owner got his land before or after the forming of the country that incorporates his land.
When it comes to tresspassers
- as the baku are - one just evicts them.