In one of the largest class actions in history, involving more than 1.5 million current and former Wal-Mart employees, the U.S. Supreme Court held that the case could not proceed as a class action because, in part, the plaintiffs had failed to show that there were issues of law or fact common to the class, as there was no evidence that Wal-Mart operated under a general policy of discrimination. Wal-Mart, Inc. v. Dukes, No. 10-277 (June 20, 2011).

Justice Scalia's majority opinion noted that the plaintiffs "wish to sue about literally millions of employment decisions at once. Without some glue holding the alleged reasons for all those decisions together, it will be impossible to say that examination of all the class members’ claims for relief will produce a common answer to the crucial question why was I disfavored." The Court noted that "[t]he only corporate policy that the plaintiffs’ evidence convincingly establishes is Wal-Mart’s 'policy' of allowing discretion by local supervisors over employment matters. On its face, of course, that is just the opposite of a uniform employment practice that would provide the commonality needed for a class action; it is a policy against having uniform employment practices. It is also a very common and presumptively reasonable way of doing business—one that we have said 'should itself raise no inference of discriminatory conduct.'" In sum, the Court agreed with Chief Judge Kozinski's dissent in the Ninth Circuit that the class members “held a multitude of different jobs, at different levels of Wal-Mart’s hierarchy, for variable lengths of time, in 3,400 stores, sprinkled across 50 states, with a kaleidoscope of supervisors (male and female), subject to a variety of regional policies that all differed. . . . Some thrived while others did poorly. They have little in common but their sex and this lawsuit.”