The U.S. Supreme Court today threw out an enormous employment discrimination class-action suit against Wal-Mart that had sought billions of dollars on behalf of as many as 1.5 million female workers.

The suit claimed that Wal-Mart’s policies and practices had led to countless discriminatory decisions over pay and promotions.

The Court divided 5 to 4 along ideological lines on the basic question in the case — whether the suit satisfied a requirement of the class-action rules that “there are questions of law or fact common to the class” of female employees. The Court’s five more conservative justices said no, shutting down the suit and limiting the ability of other plaintiffs to band together in large class actions.

The Court did not decide whether Wal-Mart had, in fact, discriminated against the women, only that they could not proceed as a class. The Court’s decision on that issue will almost certainly affect all sorts of other class-action suits, including ones brought by investors and consumers, because it tightened the definition of what constituted a common issue for a class action and said that judges must often consider the merits of plaintiffs’ claims in deciding whether they may proceed as a class.

Read this excellent Los Angeles Times editorial criticizing the Supreme Court’s decision.