From the New York Times:

'Judge Certifies Suit Accusing Wal-Mart of Sex Discrimination
The class-action lawsuit against the nation's largest private employer could represent as many as 1.6 million female employees.'

This ruling is not about the merits of the sex discrimination case itself, but about whether Wal-Mart's various stores operate as essentially autonomous businesses, or if they are getting their ideas from on high. This is relevant because if all the stores are one big business -- as the plaintiffs allege -- then female employees of all those stores can be included in the lawsuit, instead of having to hunt up a willing plaintiff from each individual store.