The Court also asked the parties to argue whether the class meets the traditional requirements of numerosity, commonality, typicality, and adequacy of representation.

On February 6, 2007, a three-judge panel of the Ninth Circuit affirmed the district court's class certification.

On February 13, 2009, the Ninth Circuit granted Walmart's petition for rehearing en banc on the class action certification.

[15][16] On June 20, 2011, the Supreme Court ruled in Walmart's favor by saying the plaintiffs did not have enough in common to constitute a class.

[17][18] The Court ruled unanimously that because of the variability of plaintiffs' circumstances, the class action could not proceed as comprised.

[19] Critics of the opinion allege that the decision makes it incredibly difficult to certify a class without a prohibitive amount of work on the part of plaintiff attorneys.