On 19 January 2010, the Supreme Court heard oral arguments in Granite Rock Co. v Int'l Brotherhood of Teamsters, 546 F.3d 1169 (9th Cir. 2008). One of the two issues on appeal is whether the federal district court has jurisdiction to determine whether a collective bargaining agreement containing an arbitration clause was formed, or if that question is for the arbitrator. The defendant labour union which had been sued for breaching the collective bargaining agreement moved to compel arbitration on the question of contract formation, arguing that the contract was never formed. The US District Court for the Northern District of California denied the motion. The Ninth Circuit, however, reversed and compelled arbitration on the ground that "an arbitrator will hear challenges to contract formation or to contract as a whole, provided that both parties have consented, in some fashion, to arbitration." The court found that the plaintiff "implicitly" consented to arbitration by suing under a contract containing an arbitration clause and the defendant "explicitly" consented by moving to compel arbitration.

During oral argument, questions focused on the relevance of a later collective bargaining agreement executed by the parties which included retroactivity clauses and a subsequent decision by the National Labor Relations Board bearing on the agreement. Justice Ginsburg suggested to the petitioner that the later contract renders it "academic" whether the court or the arbitrator should rule on contract formation because "certainly a contract was formed." The petitioner answered that the court, not the arbitrator, must decide whether the contract was formed because there was never a "clear and unmistakable agreement" to submit the question of contract formation to the arbitrator, and the question remains significant because "[t]here has to be somebody to say that." In response to the same line of questions, the respondent stated that the arbitration clause was in fact made retroactive by the later agreement and so the arbitrator should proceed to examine the merits.

The court's preoccupation with the developments after the initial collective bargaining agreement was negotiated suggests that the court may not need to decide the central issue to resolve this case, namely whether the court or the arbitrator has the authority to rule on issues of contract formation. However, should the court decide the issue, the decision could determine the competence of an arbitrator to rule where the existence of the contract is in question.