Yesterday's U.S. Supreme Court decision in Wal-Mart v. Dukes (pdf) -- the largest employment-discrimination suit ever filed in the United States -- reflects precisely the kind of overreach that makes so many of the decisions by the court's five-member conservative majority sweeping and regressive.

It's not as though experts expected that a majority of the justices would allow the case to proceed as a class action of 1.5 million women, challenging what they contend are the retail giant's discriminatory employment practices.

Class action is a procedural device that allows similarly situated plaintiffs who are injured by the same defendant to group their claims together. It allows plaintiffs, who would otherwise be unable to afford to vigorously prosecute a legitimate claim against a larger, well-resourced defendant, to aggregate their claims to achieve economies of scale.

The class action device also saves judicial resources and litigation costs for defendants by permitting them to collectively develop documents and testimony on key issues in the case. The modern class action has been especially important and, in fact, was particularly designed to advance the litigation of civil rights actions by private parties. Employment-discrimination class actions brought under Title VII of the Civil Rights Act of 1964 are among the most routine class actions.

Nevertheless, there were warning signs that the Dukes plaintiffs would not fare well with the Supreme Court. It has long been understood that the court is wary of nationwide class actions. In addition, the plaintiffs in this case had sought to have their class of women employees seeking back pay certified under the class action device -- Rule 23(b)(2) -- reserved for plaintiffs seeking to stop defendants from engaging in discrimination, rather than wanting monetary relief as the victims of discrimination.

Class actions seeking monetary relief are more often certified under Rule 23(b)(3), which requires parties seeking class certification to demonstrate that common issues "predominate" among their claims and to prove that a class action is the "superior" method of advancing the claims. These showings of "predominance" and "superiority" are generally the most difficult burden for class claimants seeking certification to overcome, and make certification under 23(b)(3) particularly challenging.

But in its decision in Wal-Mart v. Dukes, the Supreme Court did not strike down the plaintiffs' claims on the grounds that it could not advance as a (b)(2) class action and remand the case to the trial court to allow the plaintiffs to seek certification under (b)(3). Nor did the court even pre-empt the plaintiffs from doing that by merely suggesting that the plaintiffs could not meet the predominance and superiority burdens of (b)(3) certification. Instead, the court struck a blow at all employment-discrimination class actions by deciding that the Wal-Mart class action failed because it could not meet the least stringent requirements for class certification.