1. The text of the Tax Injunction Act only prevents federal courts from hearing claims that would enjoin the "assessment, levy, or collection" of state taxes, 28 U.S.C. § 1341, so this Court has twice held that the Act does not strip federal jurisdiction over claims challenging government demands for information. Direct Marketing Ass'n v. Brohl, 575 U.S. 1 (2015); CIC Servs., LLC. v. Internal Rev. Serv., 141 S. Ct. 1582, 593 U.S. ___ (2021). Here, the Online Merchants Guild challenges the lawfulness of California's demands that non-resident merchants who sold goods online through Amazon provide information to register for a California "seller's permit" or face "imprisonment for 16 months, two years, or three years." The Ninth Circuit held that this Court's precedents do not control, and the Tax Injunction Act strips federal jurisdiction, because the merchants who received the demands were putative "taxpayers" instead of "third parties." The first question presented is: whether the Tax Injunction Act applies differently based on whether the plaintiff is a putative taxpayer or a "third party."

2. As an alternative holding, the Ninth Circuit ruled that the comity doctrine supported discretionary abstention. Under this Court's precedents, federal courts may not abstain if the plaintiff lacks an adequate remedy for their federal injury in state court. Unlike the states generally, California courts are prohibited by state law from entertaining claims challenging information demands; California courts may only hear refund requests. The Ninth Circuit held that "remedy" is sufficient. The second question presented is: whether plaintiffs who cannot challenge tax information demands in state court have an adequate remedy to challenge those demands in state court.

Whether the Tax Injunction Act applies differently based on whether the plaintiff is a putative taxpayer or a third-party