Mounting a large-scale bias claim against a huge company will be more difficult in light of a Supreme Court decision that found no convincing proof of discrimination on which to allow a class action against retail giant Wal-Mart on behalf of as many as 1.6 million women.

All the justices agreed in the decision released Monday that the case couldn't proceed as a class action in its current form, reversing a decision by the 9th U.S. Circuit Court of Appeals in San Francisco. By a 5-4 vote along ideological lines, the court also said there were too many women in too many jobs at Wal-Mart to wrap into one lawsuit.

While individuals could still pursue their own cases, they would continue with the prospect of costly legal fees and long time frames and ultimately lack the power that would have accompanied the largest sex-discrimination lawsuit in U.S. history.

Two of the named plaintiffs, Christine Kwapnoski and Betty Dukes, vowed to continue their fight, even as they expressed disappointment about the ruling.

"We still are determined to go forward to present our case in court. We believe we will prevail there," said Dukes, a greeter at the Wal-Mart in Pittsburg, Calif.