The Federal Arbitration Act (FAA) provides that arbitration agreements are enforceable “save upon such grounds as exist at law or in equity for the revocation of any contract.” 9 U.S.C. § 2. Class-action bans — contract provisions that prohibit classwide proceedings, whether in litigation or arbitration — have been held to be unconscionable in some circumstances under the generally applicable contract law of some states. In this case, the T-Mobile filed a petition for certiorari asking the Supreme Court to consider whether state unconscionability law is preempted by the FAA when the class-action ban to which it is applied is embedded in an arbitration agreement. Public Citizen was co-counsel for the respondents at the cert stage, and the Supreme Court denied cert. In a later case, AT&T v. Concepcion, the Court considered this issue and ruled that mandatory arbitration provisions can be used to block consumers from brining class actions.