NAL but I don't think this is illegal, though it is a pretty large red flag that you're going to get lowballed.

Some states have required that job postings must include a pay range for the job in question, so since the company won't post the range, they refuse to hire in those states.

Not a lawyer, but this sounds shady as hell. Also probably not illegal, since they are specifically avoiding the places where it IS illegal.

There are all sorts of (backwards, ignorant) reasons why they may not want to disclose the pay rate, but it immediately puts me into the worst assumption that it's some sort of bait and switch scam. They can "unofficially" tell you what some people make, or what the mean earnings are (inflated due to a few high earners), to get you in the door, but most people won't touch that. Like MLM job where you're responsible for getting your own business. Or where you get a minimum wage base salary and a few people get huge commissions, but most barely scrape by.

It’s not laws that prevent disclosure. It’s laws that require it

states that do not currently mandate salary disclosure in job postings

other states with active pay transparency laws will not be considered at this time

The regulation require pay disclosure which is why they refuse to hire anyone from those locations.

The way they've phrased it makes it sound like they think they're sticking it to liberal states or something.

IANAL, but employment law is generally "it's allowed unless explicitly forbidden".
There is no right to be hired so they're allowed to include any limitations on who they might hire except for those that are illegal. For instance they can say "we refuse to hire people who live in Illinois" but they can't say "we refuse to hire Muslims."

Unlikely that it's actually any regulatory requirement, but I don't see anything illegal about it either (though I'm not based in the US, so I don't really know).