The U.S. Supreme Court overturned certification of a class of 1.5 million current and former female employees of Wal-Mart Stores, Inc. in the largest sex discrimination case in history. In a 5-4 decision, the Court found that plaintiffs had not cleared the "commonality" hurdle for class certification set by Federal Rule of Civil Procedure 23(a)(2), which requires parties to prove that claims of putative class members share common questions of law and fact.

Plaintiffs, current or former employees of Wal-Mart, sought judgment against the company on behalf of themselves and a nationwide class of female employees, alleging that Wal-Mart discriminates against women in violation of Title VII of the Civil Rights Act of 1964. Plaintiffs claim that local managers exercise their discretion over pay and promotions disproportionately in favor of men, which has an unlawful disparate impact on female employees.