The U.S. Supreme Court has ruled businesses facing arbitration can force customers or employees to pursue their cases individually rather than joining in a class action. The 5-4 decision reverses a California Supreme Court ruling that allowed customers to form a class with others, even if they had signed arbitration agreements barring class actions. The ruling could jeopardize a pending effort by at least 500,000 female workers to bring a class action sexual discrimination case against the retail giant Wal-Mart.