Back in 2001, there was a class-action lawsuit filed by Betty Dukes, a former Walmart employee, along with 6 others who also worked for Wal-Mart stores. The lawsuit claims that since 1998, women working for Wal-Mart stores have been paid less than men for the exact same jobs. It also claims that women are less likely to get promotions at Wal-Mart than are men.

In April of this year, a ruling by the 9th Circuit US Court of Appeals in San Francisco, said that the class-action suit (Wal-Mart Stores vs. Dukes) may move forward. Wal-mart has just appealed the ruling by the Circuit Court.

They argued, “The class is larger than the active-duty personnel in the Army, Navy, Air Force, Marines and Coast Guard combined, making it the largest employment class action in history by several orders of magnitude.”

The Supreme Court will decide on whether or not it will hear the case this fall.

If the case does go through, Wal-Mart could be held responsible for over 1 million female employees, who believe that they are owed back pay as well as punitive damages. If Wal-mart is forced to distribute this back pay plus damages in a class action settlement, it could cost the company billions of dollars. This would be the largest employment class action lawsuit in history, by far.

“It’s an extremely significant case, the rights of millions of women are at stake.” says Eric Dreiband, former Equal Employment Opportunity Commission general counsel.

Wal-Mart shares (WMT) on the NYSE were up 0.10% for the day, at the time of this article.