U.S. Supreme Court Justice Sonia Sotomayor’s sharp dissent in last week’s affirmative action ruling marked a new phase in her tenure even as it exposed a simmering rift between her and Chief Justice John Roberts Jr.

Sotomayor’s 58-page dissent in Schuette v. Coalition to Defend Affirmative Action was her first civil rights writing, and her first time reading her dissent from the bench, since joining the court in 2009.