If a matter is not arbitrable, then it may not be arbitrated.2 Arbitrability, generally, refers to the authority that an arbitrator possesses to decide a matter.3 A challenge to that authority is considered a “question of arbitrability.”4 There are three types of questions of arbitrability: (1) substantive challenges that a dispute is not arbitrable under the terms of an arbitration clause; (2) the contention that, despite substantive arbitrability, procedural circumstances exist that prevent arbitration; and (3) “post-award attacks on an arbitrator’s decision.”5 Of those three, “whether a matter is arbitrable under a given arbitration clause” has had recent developments in its jurisprudence.6 This type of challenge is referred to as “subst...