In an antitrust dispute, the parties agreed to arbitration, but did not specify whether the arbitration could include class arbitration. When arbitration is conducted on behalf of a class, the value of the claims is affected by the size of the class, and as a practical matter, the pressure on the defendant to settle is enormous. In this case, the Supreme Court decided that an arbitrator may not impose class arbitration when the parties did not expressly allow it under their agreement. A federal court had rejected class arbitration because it is not customary in the maritime industry, but an appeals court reversed, saying the law in this area is not so clear.
In its decision on April 27, 2010, the Court ruled 5-3 that imposing class arbitration on parties that have not agreed to it is inconsistent with the Federal Arbitration Act. The central purpose of that Act is to ensure that private agreements to arbitrate are enforced according to their terms. If the parties did not agree to arbitrate class action claims, arbitrators may not infer such an agreement solely from the fact that the parties agreed to arbitrate. According to the Court, "The differences between simple bilateral and complex class action arbitration are too great for such a presumption."