This is the 9th circuit case in which the circuit court found a Fourth Amendment violation based on a CPS worker and Sheriff's deputy's warrantless interrogation of a then 9-year-old at school. The 9th Circuit, though finding the violation, found that the official had qualified immunity since the law was unclear before. The deputy was granted cert in the U.S. Supreme Court.
The Supreme Court ruled it could review the appellate court's constitutional decision, even though Camreta was the prevailing party below, based on qualified immunity. Nevertheless, the Court held the case is moot, because Greene has no continuing stake in the controversy. Consequently, it vacated the portion of the 9th Circuit opinion that imposed the warrant requirement.
Justice Kagan wrote the majority opinion in which Roberts, Scalia, Ginsberg and Alito joined. Scalia wrote a concurring opinion. Sotomayor, joined by Breyer wrote an opinion concurring in the result, but opining that the court should have decided only that the case was moot and vacated the judgment below. Kennedy, joined by Thomas, wrote a dissent concluding that Camreta as a "prevailing party" should not have been permitted to appeal the constitutional decision below, which he describes as "obiter dictum".
Thanks to the NACC yahoo group for notice of and the link to the decision and to members of the group for the concise summary quoted above.