I've already mentioned I quite like this episode. I grant the creators full credit for trying to raise the bar in talking about something of substance as well as daring to have a downbeat ending where no one wins. They were emulating the best of TOS which were often dramatic moments and moral ambiguity.
That said this isn't above criticism. Beyond mere nitpicking which can be largely dismissed I do have a few reservations.
Firstly I don't mind the McKennah character. I understand she might be something of a bridge to TNG fans although, speaking for myself, a Counselor isn't something I'd have brought into the TOS era given we never saw any such thing in TMP, TWOK or later. Doesn't mean Counselors weren't in those eras, but we never saw them. Given that I credit the STC folks with making Elise McKennah a doctor. But what is she a doctor of: psychology, sociology, both, something else, what? I also question her use in this episode. Because it strikes me Uhura serving as the bridge to Lolani would have been much more dramatically effective, primarily because of what Uhura represents both today and certainly in the 1960s. As a black woman in a position of responsibility and authority she ideally illustrates how far a people can come, which would be particularly poignant given Lolani's status and situation. I also feel McKennah is being written as too forward or familiar with the command crew. No one outside of McCoy and Spock could challenge Kirk the way McKennah was shown to do. And I think Kirk should have been a little more forceful in pointing out the line she crossed. Also her presumptive familiarity bothered me---she addressed Spock without the honorifc "Mister" which struck me as again stepping over the line. It was presumptive on her part and it didn't feel right.
The other element that bugged me was the political angle. As I understand it the Enterprise is sovereign Federation territory. As soon as Lolani came aboard she came under the protection of the Federation as well as subject to its laws. She was involved in an incident involving Federation citizens (the Tellarites) and if she requested asylum as a persecuted individual Kirk has the authority to give her temporary asylum as well as detain her until he can deliver her to a starbase where all the legalities and politics would be sorted out. This is no different than the situation in "Let That Be Your Last Battlefield" where Lokai stole a Starfleet shuttlecraft and after being caught requests asylum aboard the Enterprise. Bele next arrives and claims Lokai as an escaped convicted prisoner. Because Cheron has no treaties with the Federation Bele has no grounds to reclaim Lokai and Kirk turns him down flat as well as detains Lokai to deliver him to starbase. When Bele insists Kirk contacts Starfleet who backs him up. So Lokai stole a shuttlecraft and Lolani might have murdered Federation citizens, both incidents the Federation has the right to investigate before entertaining any thought of releasing those individuals. And the Federation has no treaties with Cheron or Orion. So what's the difference? Why is Starfleet willing to back Kirk up over a stolen shuttlecraft but not over a possible homicide? To me it doesn't wash.
How it should have played out was the Orion slaver showing up to claim his "property" and Kirk turning him down flat and informing him he could settle it at starbase, but until then Lolani was detained as well as under Federation protection. And it looked like Kirk was fully prepared to do just that until Starfleet (in the person of Commodore Gray) overrides him and orders him to release Lolani back to the slaver. For me this is a genuine WTF! moment that really makes Starfleet look bad because they're not even willing to have have a proper inquiry over the incident when previously they were insistent on Lokai being returned to starbase for a full inquiry into stealing a shuttlecraft.
What this says to me is that there might have been something else going on that we and the Enterprise crew are not aware of. Maybe the Federation was in negotiations with Orion for something or other and didn't want this incident rocking the boat so they order Starfleet to give Lolani up. Again, though, that makes the Federation look bad and yet nothing of this kind of background is mentioned even in a passing reference to clue us in as to why Starfleet is so willing to surrender a woman back into brutal slavery.
Raising these points is not meant as a slam of the episode as a whole. I raise them as an observation of what I see as inconsistencies in terms of story and continuity. Something to think about.