You can find the Supreme Court’s decision, along with separate opinions of Justice Barrett, and Justices Kagan, Sotomayor, and Jackson (together) at this link. [This post is in progress]
The Court unanimously agrees that states cannot enforce Section 3 disqualification against federal officers, citing a number of reasons including the problem of patchwork enforcement and uncertainty as to the standards of proof etc. States remain free to remove state offers on this ground.
On this point the Court is unanimous. The opinion is unequivocal and so all efforts to remove Donald Trump from the ballot on grounds he participated in insurrection are invalid. There will be no more successful litigation on this point this year. In places where he has been removed, he must be put back on the ballot.
But this is where the agreement among the justices ends. The Court majority goes out of its way to impose some very severe limits on how Congress may enforce Section 3 against an insurrectionist. This is complete dicta: that is, none of this was necessary to include to decide that a state cannot disqualify a federal officer under Section 3.
In particular, the majority requires a certain kind of procedures that Congress must follow (see page 5 of the opinion) and that the remedy that Congress pursues must be “congruent and proportional” to Congress’s power to enforce the 14th amendment. As Justices Sotomayor, Kagan, and Jackson explain, this gives the Supreme Court major power to second guess any congressional decision over enforcement of Section 3. Nothing in Section 3 supports these limits or procedures, the liberal Justices say (and they are right).
What this means is that if Congress tries to disqualify Trump, either before or after the election (which Congress may well try to do), the Supreme Court will have the last word on doing so. We may well have a nasty, nasty post-election period in which Congress tries to disqualify Trump but the Supreme Court says Congress exceeded its powers.
[This post has been updated]