This split decision holds that when the case is in federal court under their federal question jurisdiction, federal common law, rather than the law of the state or foreign country in which the contract was entered into, governs threshold questions of arbitrability, such as whether a nonsignatory to the arbitration agreement may enforce it through equitable estoppel.  Under federal common law, equitable estoppel allows a nonsignatory to enforce an arbitration agreement only if the claims in suit are intertwined with the contract that contains the arbitration agreement.  Here, the panel concluded that the claims were not so intertwined, so the motion to compel arbitration was properly denied.