Rule 23 class actions made headlines earlier this summer with the Supreme Court’s June decision in Trump v. CASA, Inc. The case is substantively about birthright citizenship and the validity of Executive Order No. 14160, which attempts to eliminate birthright citizenship in violation of the Fourteenth Amendment, federal statute, and decades of legal precedent.

But the appeal heard by the Supreme Court in May wasn’t about birthright citizenship at all. Instead, it asked whether federal judges were empowered to order defendants to modify or stop unlawful behavior, policies, or practices generally and not just for the parties in the lawsuit. These types of orders are known as national or universal injunctions, even though their scope isn’t necessarily nationwide or universal.