The SCOTUS 9-0 decision tells me that a state can’t decide a national election by banning a candidate then the state has an obligation to see to it that only properly registered voters cast a ballot. Shouldn’t the Federal Election Committee be able to compare voter rolls in every state? People voting in multiple states has long been reality.
I think that is one of the best ways to keep the voter rolls clean would be to purge all voter registrations six months after every Presidential election.
People would then be required to physically show up and re-register. Too lazy to register...your probably too lazy to be familiar with the issues. The trick will be to ensure that every state registration location is actually following the law regarding registration.