A major U.S. Supreme Court recently reversed The Ninth Circuit to not recognize about 1.5 million female employees at Wal-Mart stores. The workers sued Wal-Mart, collectively, for sex discrimination in pay, promotions, and other employment practices. The Wal-Mart ruling did not examine whether the claims had merit or not, but rather the Court concluded that each plaintiff will have to pursue her claim individually.
The decision was 5-4, with the traditionally conservative and liberal justices (Supreme Court judges) opposing one another. The dissenting four justices concluded that the "practice of delegating to supervisors large discretion to make personnel decisions, uncontrolled by formal standards" was enough to unify a group of plaintiffs for a common question as demanded under Federal Rules of Civil Procedure 23(a).
The majority implied that if a company has a written policy that forbids sex discrimination, then this policy may protect the company.