The Federation had no claim for eminant to a planet that was already inhabiated, calimed by another race before the Federation was estalished.
That presumes that the Federation recognizes the ring planet as the Baku's private property. The Baku are relatively few in number, and they are not indigenious to that planet. The Federation could easily not view them as the planet's "owners."
Exercising eminant domain might not have been seen as necessary.
... the briar patch, before belonging to the federation, belonged to one of its member species or to someone else who gave it to the federation by treaty/etc ...
According to ENT (augment arc) when the Baku arrived the briar patch and it's contents was Romulan territory. Later it somehow passed into the hands of the Klingons (per DS9). Later still it passed into the hands of the Federation.