They split the baby here and allowed the law to take effect for state and local elections, but not the presidential race.
It could have flipped the state to Trump if they allowed the law to take full effect as there are tens of thousands of Arizona voters that are so-called "federal only" voters. They would have had their registration invalidated.
Justices Clarence Thomas, Samuel Alito and Neil Gorsuch would have allowed it to take full effect.
Justices Sonia Sotomayor, Elena Kagan, Ketanji Brown Jackson, and Amy Coney Barrett would have rejected it in full.
Still highly unusual. Under the Purcell Principle, SCOTUS normally avoids meddling in election rules if the election is near.