The Ninth Circuit has upheld the class certification decision of the district court in Dukes v. Wal-Mart. Wal-Mart class action.pdf
The class in this case is all of the women who have worked for Wal-Mart or Sam's Club at any point since 1998--an estimated 1.5 million women. The allegations in the complaint are that because of the centralized control of the main office and the policies it implemented, all of those women were discriminated against in pay and promotional opportunities in the same way.
This is structural litigation at its most basic even though it's directed at a private company and not the government.