Plaintiff Timothy Sandquist and the various defendants here are parties to an arbitration agreement. A salient question is whether that agreement permits or prohibits arbitration on a classwide basis. Here we must answer a question one step removed—who decides whether the agreement permits or prohibits classwide arbitration, a court or the arbitrator? The question has divided the many state and federal courts to consider it.
We conclude no universal rule allocates this decision in all cases to either arbitrators or courts. Rather, who decides is in the first instance a matter of agreement, with the parties’ agreement subject to interpretation under state contract law. Under state law, these parties’ arbitration agreement allocates the decision to the arbitrator. Under federal arbitration law, no contrary presumption requires a different result, so the issue remains one for the arbitrator. Because the Court of Appeal arrived at a similar answer, we affirm.