It's a 9-0 decision on the basis of the fact that states can't kick someone off the federal ballot. Enforcement against federal offices have to come elsewhere.
Barrett makes a concurring opinion about how great it is that the Supreme Court came to a unanimous decision on this.
Sotomayor, Kagen, and Jackson issue a concurring opinion of substance: that the majority opinion shuts the door to avenues of enforcement at the federal level besides Congress, and that's a problem.
All states currently have their own rules regarding who can be on a presidential ballot. Did SC just give that power to Congress?
For all intents and purposes, I believe so. But one of the points that actually got a laugh in the oral arguments was how divided (ineffective) the Congress is.
Well, as one judge said to the other, 'Be just and if you can't be just be arbitrary.'