In light of the U.S. Supreme Court’s decision Monday in Ramos v. Louisiana, in which it held that the federal Constitution forbids states from convicting defendants except by a unanimous jury, Cornell law professor Michael C. Dorf discusses the Court’s jurisprudence on retroactivity. Dorf highlights some costs and benefits of retroactivity and argues that the Court’s refusal to issue advisory opinions limits its ability to resolve retroactivity questions in a way that responds to all the relevant considerations.