Courts, not arbitrators, must decide which of two contracts between the same parties–one with, the other without an arbitration clause–governs a particular dispute.  This is true even when the arbitration clause in the one contract containing it has a strong delegation clause, leaving to the arbitrator all arbitrability questions.  Here, Coinbase had a basic customer agreement with an arbitration clause but then also sponsored a contest with its own contract with contestants which did not contain an arbitration clause.  A court had to decide whether the customer’s complaint was governed by the contest contract or the basic customer agreement.