"Personae Non Grata" struck me as a mostly good if uneven episode, with one half being better than the other and one key relationship being still bland but also with a great guest turn. It's not a novel scenario here or a theme that is new, but the topic is hardly irrelevant and does hit hard when done right. As has been said with many other episodes of 'Law and Order', the show has proven many times at doing wonders with familiar or basic stories.
While not quite fitting this distinction, "Personae Non Grata" was pretty much what was remembered from first watch. So a good episode, but not a great one with a mix of good and not so good (thankfully more of the former) and very much worth seeing for the guest star (Melissa Leo in her third of three 'Law and Order' appearances) primarily. As far as Season 18 goes, its penultimate episode is neither one of the best or worst and is one of the solid middle ones.
Not everything works. The first half is inferior to the second, not just because of the predictability but also the chemistry between Lupo and Bernard is still rather bland to me. Lupo also doesn't have the spark that he had when he was partnered with Green and is always overshadowed by the more animated Bernard.
It is another episode that could have benefitted from a less "wrap as much as we can up with five minutes to go" sort of conclusion. It's all well staged, written and acted, the truth just needed longer to unfold.
However, a lot works really well. It is shot with the right amount of intimacy without being claustrophobic and that the editing has become increasingly tighter over-time has been great too. Nice use of locations too. The music doesn't get over-scored or overwrought, even in the more dramatic revelation moments. The direction doesn't try to do too much and is understated but never flat or unsure.
The script is lean and thought-probing with the right amount of grittiness. The story is riveting in the second half and is intricate and tense without being over simple or too complicated. The acting is very good, especially in the second half. With Leo at her most monstrous, and chilling at that, coming out on top.
Concluding, good but not great. 7/10.