Ever since U.S. District Judge Martin Jenkins of the Northern District of California certified a class action of sex discrimination claims against retail giant Wal-Mart Stores in Dukes, et al. v. Wal-Mart Inc. on June 22, employers and their in-house lawyers have focused on how to avoid being the next target of a major class action.

Although the district court’s 82-page opinion contains numerous legal points, general counsel intent on avoiding the next Wal-Mart class certification should focus on the court’s discussion of the commonality requirement for class actions.

According to the court’s opinion, Wal-Mart defended the motion for class certification by arguing that, with more than 3,400 stores and more than 1 million employees, the promotion and pay decisions in question were subjective in nature and therefore not common to all members of the class.

While subjectivity in employment decisions usually is not a good defense to liability in an individual discrimination case, the existence of such subjectivity can help prevent class certification.

In Dukes, however, it was precisely such subjectivity that landed Wal-Mart in hot water. Here’s how GCs can help their companies avoid some of the mistakes that led to certification of the Wal-Mart class.