Last week the Supreme Court passed up an opportunity to resolve a hotly disputed aspect of employment arbitration law: Whether judges or arbitrators should decide whether class (or collective) arbitration is available when an arbitration agreement is silent on the subject.  The Court’s denial of certiorari in Opalinski v. Robert Half International, Inc., 583 U.S. — (No. 16-1456) (Order List of October 30, 2017, p. 10) thus put a precipitous and somewhat unexpected end to a bit of suspense about this case over the last few months.  While the arbitration spotlight is currently focused on the Court’s consideration of whether enforcement of class arbitration waivers violate the National Labor Relations Act, see, Epic Systems Corp. v Lewis, No. 16-285 (argued in tandem with Ernst & Young LLP v. Morris, No. 16-300 and N.L.R.B. v. Murphy Oil USA, No. 16-307 on October 2, 2017), lurking in the shadows is a corollary issue presented in Opalinski:  What happens when an employment agreement specifying arbitration does not contain such a class action waiver?  That is, if an agreement says nothing about class arbitration one way or the other, who decides whether class treatment is permissible?  More precisely, is class treatment a procedural question for an arbitrator or is it a gateway arbitrability question for a judge to decide?