But the court's four-member liberal bloc, in partial dissent, said the 1.5 million putative women in the class should have been given a chance to show there was enough "commonality" in their situations to qualify as a class.
Justice Ruth Bader Ginsburg, who practically argued the concept of gender discrimination into law as an attorney in the 1970s, said in her partial dissent the majority "disqualifies the class at the starting gate, holding that the plaintiffs cannot cross the 'commonality' line set by" the Federal Rules of Civil Procedure.
The case started in San Francisco in 2001 when six women filed suit claiming Walmart discrimination, in part because they were passed over for promotion in favor of men.
"This nationwide class includes every woman employed for any period of time over the past decade, in any of Walmart's approximately 3,400 separately managed stores, 41 regions and 400 districts, and who held positions in any of approximately 53 departments and 170 different job classifications," the company's petition to the Supreme Court said. "The millions of class members collectively seek billions of dollars in monetary relief under Title VII of the Civil Rights Act of 1964, claiming that tens of thousands of Walmart managers inflicted monetary injury on each and every individual class member in the same manner by intentionally discriminating against them because of their sex, in violation of the company's express anti-discrimination policy."
A federal appeals court panel and the full 9th U.S. Circuit Court of Appeals, both divided, approved the certification of the class.
In the majority opinion written by Justice Clarence Thomas, the justices said when plaintiffs seek individual relief such as back pay or reinstatement, the company has "the right to raise any individual affirmative defenses it may have, and to 'demonstrate that the individual applicant was denied an employment opportunity for lawful reasons.'"
The appeals court tried to replace this procedure with a "Trial by Formula," the opinion said, using a "sample set," with the result applied to the huge class. "We disapprove that novel project."