Not sure I understand?
American Goshawk is a new name for a split species so should be fine?
Western Flycatcher, the name existed previously, common sense says that reverting to Western Flycatcher, isn't or shouldn't be a problem.
You can see my thoughts above referring to the goshawk.
You do make a good point about Western Flycatcher using one interpretation of the law - and I'll use this as an opportunity to take another potshot at it.
The law says: "The division shall use the English-language name assigned to a bird by a naming entity that was in effect on January 1, 2020, when using an English-language name while engaging in the management of the bird or habitat for the bird."
Splitting apart this sentence, does it mean "The division shall use the English-language name... that was in effect on January 1, 2020?" If so, no Western Flycatcher - it was not in effect on that date and no "bird" was named "Western Flycatcher" by a qualifying entity on that date. And also, of course, no Thick-billed Longspur - it is McCown's just as it was on January 1.
If instead, the sentence means "The division shall use the English-language name assigned... by an entity that was in effect on January 1, 2020," then Western Flycatcher is absolutely valid as a name that was assigned by the qualifying entity, the AOS, which was in effect on the required date - even if the name was not in effect. However, that would also mean that "Thick-billed Longspur" is a valid name, as it is assigned to the bird by the same entity, and also on a different date. You and I both know that this is hardly likely to be the intent of the law... but it is indeed a valid interpretation at the very least until a judge makes and publishes a ruling on the legal intent.
A carefully worded law would have made clear whether the important thing to be in effect on January 1, 2020 is the "name assigned to a bird" or a "naming entity." Now to be fair, the next line 23A-12-102.(2)(b) seems to associate the date with the assignment, so points the law towards the first interpretation even if not explicitly.
The point stands that the rule could have simply stated something to the effect that "the state of Utah does not accept changes in bird names due solely to removing eponyms and won't put such changed names in state publications" - certainly put more elegantly than I did, but I think you can see what I mean. Its difficult for me to believe that the language is accidentally vague when such obviously simple alternatives can be reached.
You may validly be asking why anyone should care. A messy rule like this can develop a life of its own in a litigation-happy country such as the U.S. We also have a very beloved Second Amendment to the Constitution - the freedom of any individual to articulate ideas without threat of retaliation or legal sanction from the government. That freedom extends to employees of Utah's Division of Wildlife Resources. If I were a lawyer who wanted to make a name for myself in Utah, and I could find a UDWR employee who wants to make a statement - this is a ripe rule to make a fuss and potentially a lot of money over. Think of the national and international attention! (but don't think about the effects on birdlife, conservation, or expenditures please, nor the actual topical issues that people are very passionate about!)