Kentucky’s attorney general sought to intervene in an appeal defending a state law that regulated dilation-and-evacuation abortion procedures. The attorney general’s office had earlier agreed to dismiss claims against him while reserving rights in any appeal, and the state cabinet secretary continued defending the law. After the Sixth Circuit affirmed a permanent injunction and the secretary declined to seek further review, the attorney general moved to intervene and filed a rehearing petition. The Sixth Circuit denied intervention. The Supreme Court reversed. It held that no statute or rule made the attorney general’s intervention motion jurisdictionally barred merely because he had not filed a separate notice of appeal, and that ordinary intervention principles governed the request. The Court also concluded that the attorney general had a significantly protectable interest, that the motion was timely under the circumstances, and that existing parties would not suffer undue prejudice. The Court remanded for the court of appeals to exercise its discretion under the correct framework. Justice Sotomayor dissented, emphasizing the attorney general’s earlier litigation stipulation and the need to protect reliance and finality.