Costco...won a court decision that blocks women who accused the company of gender bias from suing as a group, but the court left open the possibility that the case could regain class-action status. The case involved about 600 current and former female Costco workers who said the largest U.S. warehouse club chain made it harder for them to be promoted to general manager or assistant general manager...Citing a recent U.S. Supreme Court ruling in favor of Wal-Mart Stores...the...Court of Appeals...said a lower court judge...failed to decide whether there was enough in common among the women's claims...[T]he...court returned the case to U.S. District Judge Marilyn Hall Patel...to decide whether she could still certify a class...Jocelyn Larkin, executive director of The Impact Fund, which handled the case for the women plaintiffs, said "we are absolutely delighted" with the...decision...Joel Benoliel, Costco's chief legal officer, said: "We are extremely gratified that our major points in the case have been vindicated, and it's clear the court has shut the door on a nationwide class..."