No, its not eminent domain doesn't work that way.
For all we know, it is exactly how eminent domain works in the 24th century Federation.
That doesn't exactly disprove my point that the TNG Federation is acting like Russia under Putin in this movie.
In fact it's just the opposite.
What with eminent domain of today requiring a legal proceeding which in part (from the sounds of it) finds out if a government can actually seize the piece of land in question and makes sure the owner is given just compensation.
You can find out about that stuff here
So I don't really see why the federation would change to a version that shits on due process rights.
Actually cut the Son'a out, keep the rings, and have Starfleet Medical/Commandpushing to use the planet to house war refufess/wounded cause of the rings' healing properties. Kick the Baku down to a very primitive, tribal, native born race, and removing them from the planet will kill them.
And they couldn't set up the hospital refugee center on the other side of the planet why exactly?