The policy rationales that underpin enforcing arbitration agreements may potentially be at odds with those underpinning the class actions regime (see our previous posts here and here). These policy rationales collide when confronting the question of whether plaintiffs can waive their right to participate in a class action through a mandatory arbitration clause and, if so, when this is permissible. Canada and the United States continue to have different approaches to the question of who decides whether a dispute is arbitrable – the arbitrator or the court? With respect to enforcement in the class action context, courts in the United States tend to enforce arbitration clauses such that class actions are precluded. However, in Canada an arbitration clause that acts as a barrier to dispute resolution may be unenforceable and precluded by certain legislation.