what could they be compelled to stop doing here? Mechanically speaking, I mean. I can imagine fines or contempt of court, etc
But how would you remove an international distro from "the marketplace" if it's free and not operating a business?
If anyone is distributing it within Illinois jurisdiction (or maybe even distributing it elsewhere while maintaining a business presence in Illinois), they could be at risk of qualifying as an operating system provider under Illinois law.
Same way anything else gets pulled from distribution. You shut down the servers, destroy keys, remove files, etc. Sure, the files may remain in circulation from unofficial sources, but that's not your problem, as long as you're no longer facilitating it.
It's not that complicated.
If there's a law that says "Anyone who distributes X must also Y" and you can't figure out a way to continue distributing X while also doing Y, the way you comply with the law is that you stop distributing X.