They say that the plaintiffs lack standing. This case shouldn't have gotten this far in the first place.
Alito, Gorsuch, and Thomas dissent.
This case ironically had an enormous amount of misinformation make it into the record. Which seems to be a pattern of late.
Barrett in her opinion notes these false claims in her opinion: "The Fifth circuit relied on the District Court's factual findings, many of which unfortunately appear to be clearly erroneous".
I'm deeply cynical about how the justices arrive at their opinions. But I am distinguishing that from political partisanship versus like conservative originalist hackery.
Like, Gorsuch is basically just making things up as he goes these days. But I don't think he's doing it for the GOP.