In a proceeding under 9 USC 7 to enforce a subpoena that an arbitrator has issued to a non-party witness, when no federal claim is at stake, a federal court has jurisdiction over the matter only if the requirements for diversity jurisdiction (including the amount in controversy requirement) are satisfied. The amount in controversy exceeds $75,000, if the value of enforcement of the subpoena–the value of the thing to be accomplished–is equal to $75,000 to anyone concerned in the action. Here, the subpoenaed party said it would spend less than $2,000 in complying with the subpoena. However, Maine Community presented expert evidence to substantiate its assertion that getting the subpoenaed documents would help it prove at least $75,000 of its $17 million claim against the other party to the arbitration. Hence, the federal district court had diversity jurisdiction of the subpoena enforcement proceeding.